Physics quiz question: object inside converging lens focal point

Physics 205B Quiz 2, spring semester 2020
Cuesta College, San Luis Obispo, CA

An object 1.0 cm in height is placed 16 cm in front of a converging lens with a focal length of +25 cm. The resulting image is:
(A) upright, diminished.
(B) upright, enlarged.
(C) inverted, diminished.
(D) inverted, enlarged.
(E) (No image would be produced.)

Correct answer (highlight to unhide): (B)

Solving for the location of the image d_i:

(1/d_o) + (1/d_i) = (1/f),

(1/d_i) = (1/f) – (1/d_o),

(1/d_i) = (1/(+25 cm)) – (1/(+16 cm)) = –0.0225 cm^–1,

d_i = 1/(–0.0225 cm^–1) = –44.444... cm,

where the negative sign by convention makes this a virtual image located to the right side of the lens (the side of the lens opposite the original object). The linear magnification m is given by:

m = h_i/h_o = –d_i/d_o = –(–44.444... cm)/(16 cm) = +2.777...,

which means that this virtual image is upright, due to the positive sign, and is enlarged, being about 2.8 times the size of the original object.

Sections 30882, 30883
Exam code: quiz02B3rD
(A) : 1 student
(B) : 21 students
(C) : 3 students
(D) : 10 students
(E) : 0 students

Success level: 60%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.83

Physics quiz archive: lenses, optical instruments

Physics 205B Quiz 2, spring semester 2019
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz02B3rD



Sections 30882, 30883 results

0- 6 :
7-12 :	*** [low = 7]
13-18 :	*****
19-24 :	********************* [mean = 21.5 +/- 5.2]
25-30 :	****** [high = 30]

Online reading assignment: history of astronomy, telescope powers (SLO campus)

Astronomy 210, spring semester 2020
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on reviewing the history of astronomy, Kepler's and Newton's laws, and telescope powers.


Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"The progression of ideas and theories and how astronomers figured them out through time."

"The different ancient astronomers' ideas about how the universe worked was very interesting, how some were based on science but some were completely not science-based, but were still believed since they were based on first principles."

"I enjoyed reading about the history of each of the early astronomers and the contributions they made to helping demystify the universe. It was interesting to me personally because I am a storyteller, so hearing peoples stories is far more engaging for me than reading the theories."

"I found it interesting that all the astronomers were a part of the Renaissance. We typically look at the Renaissance as a time of art, but it also was a time for questioning the foundation of what we had."

"The way planets orbit and how Kepler and Newton managed to figure out how and why planets move in certain way, and why planetary motion could tell us do much about the laws of the gravity apply to Earth folks and the notion of outer space. "

"I found Newton's laws and Kepler's laws to be very interesting. I think it is crazy how they came up with all these theories regarding the planets and motion."

"I found the history of astronomy interesting, because it makes it more applicable to everyday life. A lot of times learning about science makes it seem like the scientists who discovered what we know today were less human because of all the things they discovered. But reading about how long it took and how many revisions it took for astronomers to get it right, makes it easier to follow."

"Kepler's second and third laws, it reminded me of how when I play video games like Mario Cart I try to find the closest spot to the inner track so that I can take the fastest route."

"The visuals for Kepler's laws, because the orbit of the plants seemed random before I took this class."

"Galileo's observation that added to the understanding of Earth's revolution is interesting. The fact that other planets like Venus and Jupiter go around the sun aids in the understanding that Earth can revolve around the sun without losing the moon as well."

"That basically everything I had known about Galileo was wrong. He wasn't the first person to invent or even use a telescope. He just built it himself, and got credit for it."

"That before the technology like telescopes and cameras, astronomers dedicated their lives to studying and tracking the motion of the plants with just their naked eye. It is incredible to think about how much work was necessary to understand what we do now, and more so how the studies were so in-depth that the teachings were passed through lifetimes, such as Kepler picking up where Tycho left off."

"When an object orbits earth, it's like they are constantly falling around Earth because Earth's gravity is pulling them in, but they are traveling fast enough to not fall into the ground."

"Learning about telescopes from the textbook. I own a telescope and have always been interested in them and wanted to know how they worked and how you use them. And learning about the different pieces and how they are used and what they are used for was very helpful. Learning about the mirrors, the way light reflects and the primary lens was very helpful and I can apply that in my life which is great for me."

"I thought learning about how telescopes work was interesting. Like how, rather then just zooming into the sky, it captures light."

"One of the many things I personally found interesting was that magnifying power isn't as important as I thought it was for telescopes. I believed that magnifying power was very important because of the close view we got to see when seeing the moon through the telescope."

"It was interesting learning what to look for when picking out a telescope. I always thought the bigger the telescope the better, but it's more like the bigger the primary lens or mirror the better."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"Retrograde motion was confusing for me."

"I find the history portion of this week's readings a little confusing because history is not my best subject."

"I think trying to remember the different ideas and models of each astronomer and also how others incorporated or used the ideas of others and formed their own work out of it will be something that I need to focus and study on."

"I had a very difficult time understanding the theories and laws. For instance Kepler's laws: ellipses, semi-major axes and eccentricities--I couldn't begin to explain what those are about. It has to do with how I learn, I have a difficult time understanding concepts like this just by reading them. I need them explained, broken down, pictures, example, etc."

"Kepler's laws and how they work."

"I found Kepler's second law confusing. I read the explanation in both the book and online presentation and I'm still not quite getting it. I feel like I almost understand, but not enough to explain it to someone else."

"I think I am struggling most with grasping Kepler's second and third laws. My understandings from the text itself are very vague, but I am hoping the topic will be clarified during lecture or in assignments. The diagrams for the first law helped me understand better, so not having visuals for the second and third are what I believe is causing me confusion."

"Newton's cannon kind of confused me, like the paths the cannonball takes."

"The electromagnetic spectrum a bit confusing. It is just very hard for me to conceptualize everything and understand the vocabulary terms."

"I feel like I will struggle to remember everything about the telescopes."

"The telescope stuff! So much terminology and it's hard just reading straight from the book, without being able to visualize it in person."

"I'm having a hard time understanding all of the parts of a telescope and how they work together so we can see a magnified version of a far away object. I'm sure once we're in class and actually using telescopes I'll understand them because I'm more of a kinetic learner."

"I don't really understand the difference between D, f_primary, and f_eyepiece. They all seem pretty similar to me and I get a little confused trying to figure out which is which."

"I didn't find anything confusing, I actually understood the chapters."

"There wasn’t anything confusing to me."

"I will read it all tomorrow before class."

When a planet is undergoing retrograde motion, over several nights it moves __________ with respect to the background stars.

east to west.	***************** [17]
west to east.	*********** [11]
(Unsure/lost/guessing/help!)	******* [7]

When a planet is undergoing prograde motion, over several nights it moves __________ with respect to the background stars.

east to west.	********** [10]
west to east.	**************** [16]
(Unsure/lost/guessing/help!)	********* [9]

Categorize each of Kepler's laws.
(Only correct responses shown.)

Kepler's first law: describes the shape of a planet's orbit. [80%]
Kepler's second law: describes the speed of a planet along its orbit. [77%]
Kepler's third law: describes the speed of a planet along its orbit. [51%]

Categorize each of Newton's laws.
(Only correct responses shown.)

Newton's first law: relates forces with changes in motion. [57%]
Newton's second law: relates forces with changes in motion. [69%]
Newton's third law: describes a property of forces. [63%]

The __________ power of a telescope depends on the: (Only correct responses shown.)

light-gathering: diameter of the primary lens/mirror [54%]
resolving: diameter of the primary lens/mirror [63%]
magnifying: both the focal lengths of the primary lens/mirror and eyepiece: [69%]

The least important feature to consider when purchasing an optical telescope is the __________ of its images.

brightness.	*** [3]
resolution.	* [1]
magnification.	********************** [22]
(Unsure/lost/guessing/help!)	********* [9]

Briefly explain your answer for the least important feature to consider when purchasing an optical telescope.

"Magnification is the least important feature to consider when purchasing an optical telescope because higher magnifying power does not mean that there is more detail."

"I think the magnification feature is the least important feature. The magnification feature only enlarges the images after the fact. If the telescope doesn't have good brightness or resolution feature, then dim, fuzzy pictures will be enlarged."

"Just because you make something bigger, doesn't mean that it provides a clearer picture."

"Not sure."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Can you please explain what prograde motion is? Is it just once a planet is no longer in retrograde it goes back to prograde and does that mean it moves the normal west to east direction in the sky? Or something else?" (Yes, and Yes.)

"Why don't we feel the movement of Earth?" (You can--you would need very sensitive and/or large-scale experiments to detect Earth's motions. The sway of a long pendulum will drift over several hours, which measures the rotation of Earth about its own axis; and the directions of starlight changes slightly over many months, which measures the revolution of Earth around the sun.)

"Why can't the sun be at the center of an ellipse?" (A flattened circle would just have one "center"; but an ellipse officially has two foci, or two "centers," with the sun located at one focus (while the other focus is empty!).)

"Newton's second law: exerting a force (such as gravity) on an object (such as a planet) will change its motion. The more force you exert, then the object's motion will change more. I found this to be interesting because in sci-fi movies there's always some catastrophe happening in space and I always wonder if that was accurate or not. Is there gravity in space?" (Yes, there is gravity in space, which changes the motion of objects. If you're near a planet or a star, then the gravity will affect your motion by pulling you in, and/or forcing you into a closed/open orbit. Only if you are really far away from any planet or star will there be no gravity (or a negligible amount) to affect your motion.)

"Is a telescope's size measured by focal length or by lens diameter. The text doesn't appear to say." (Both "sizes" are important. We'll be sure to carefully distinguish between them in class.)

"Do you own a telescope at home? If so, how often do you use it?" (No, because I can use Cuesta College telescopes whenever I feel like it.)

"Struggling in this class because everything makes sense in lecture, and then nothing makes sense when I'm home...I'd benefit from reviewing things again. It's also hard to conceptualize these ideas (stars, moon phases, etc) and not be able to make it make sense in real life." (I think that's pretty normal. Just keep letting me know in these reading assignments what you're having problems with, so we can get these cleared up when we're in class. Also, email me or come into office hours if you have specific questions, and you can also drop in and see the embedded tutor at the Student Success Center.)

"I feel I can only partly understand topics through the textbook itself, and instead am relying on class lecture for clarification. Do you have any tips for reading that would help make the topics more clear?" (The textbook does make for some pretty thick reading. Don't worry if it all doesn't make sense the first time you go through it; also look at the blog presentations (which emphasize the important topics) and the quiz question packets (which are examples of what you are responsible to know for the quizzes) and then go back through the textbook chapter again. Multiple read-throughs are going to be typical for a lot of these chapters, but hopefully they will make more sense each time you go through them again. Just allow yourself time to visit the textbook multiple times.)

"Do astronomers know when precession will change the north star again and what star will be the new north star after Polaris?" (Because of precession, after Polaris, in a few thousand years Gamma Cephei will be the next official north star.)

"Do you believe the Mercury retrograde can affect how people act and feel?" (I'm going to defer to what my Magic 8-Ball® says.)

"I had no idea that it was the phases of the moon that primarily controls the tides. I honestly did not know how any of it worked. Will we learn more about how gravity from the sun and moon affects the tides?" (Actually that would be a very technical topic we don't have time for in this class, but the textbook gives a nice graphical summary of the concepts involved. Instead concentrate on how Newton's laws and gravity are used to explain planetary motion (although Newton's laws and gravity can be used to explain lots of other things such as tides).)

"No comment." (You just did.)

Online reading assignment: history of astronomy, telescope powers (NC campus)

Astronomy 210, spring semester 2020
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on reviewing the history of astronomy, Kepler's and Newton's laws, and telescope powers.


Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"I find the strange patterns we see in the moment of planets when viewed from an also moving Earth to be fascinating."

"That planets go through retrograde because before this class I had no idea that the planets can go the opposite way for a bit of time."

"The phases that Venus undergoes, when it's going between the sun and Earth."

"Kepler's laws and Newton's laws--I think it's interesting overall to read about how much astronomy has evolved and to learn about those who affected astronomy in large ways and how they affected science."

"Newton's cannon was super-interesting, because it could debunk the theory of flat Earth."

"What I thought was cool was learning about Galileo in this text versus in my philosophy class. I was told he invented the telescope but as I just read that is not true."

"I didn't know that light could travel through a vacuum. I thought this was interesting because I thought it would behave like sound and not be able to travel through it."

"How magnifying power was the least important power for a telescope."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"Retrograde motion and prograde motion. I just hard time remembering which one goes west and which one goes east."

"The concept of ellipses remains a bit confusing to me."

"I liked learning about telescopes, but there were some things I didn't really understand."

"How to identify whether or not a telescope was a refractor or reflector, and how to measure the f_primary, and I was wondering if that would be the same for those two types of telescopes."

"What I found a bit confusing was the types of telescopes. I think I found this confusing because there are so many new terminological definitions to remember and having to distinguish them from one another. Mainly, it's new terminology to get used to that I might have to go over more."

"Honestly, all the reading was confusing because there was a lot of info being thrown at once."

"There was no content that I found confusing from this assigned reading or presentation."

When a planet is undergoing retrograde motion, over several nights it moves __________ with respect to the background stars.

east to west.	************ [12]
west to east.	********** [10]
(Unsure/lost/guessing/help!)	*** [3]

When a planet is undergoing prograde motion, over several nights it moves __________ with respect to the background stars.

east to west.	************ [12]
west to east.	********* [9]
(Unsure/lost/guessing/help!)	**** [4]

Categorize each of Kepler's laws.
(Only correct responses shown.)

Kepler's first law: describes the shape of a planet's orbit. [88%]
Kepler's second law: describes the speed of a planet along its orbit. [80%]
Kepler's third law: describes the speed of a planet along its orbit. [56%]

Categorize each of Newton's laws.
(Only correct responses shown.)

Newton's first law: relates forces with changes in motion. [32%]
Newton's second law: relates forces with changes in motion. [56%]
Newton's third law: describes a property of forces. [52%]

The __________ power of a telescope depends on the: (Only correct responses shown.)

light-gathering: diameter of the primary lens/mirror [52%]
resolving: diameter of the primary lens/mirror [64%]
magnifying: both the focal lengths of the primary lens/mirror and eyepiece: [56%]

The least important feature to consider when purchasing an optical telescope is the __________ of its images.

brightness.	**** [4]
resolution.	[0]
magnification.	****************** [18]
(Unsure/lost/guessing/help!)	*** [3]

Briefly explain your answer for the least important feature to consider when purchasing an optical telescope.

"Magnification will make the image larger and becomes much more faint."

"Magnification enlarges any distortions due to the telescope and atmosphere."

"Optical telescopes are meant to gather visible light, so it makes sense that brightness and resolution are needed in order to see that, I'm not sure if magnification is as important, but I'm also not 100% that my answer is correct."

"Magnification because it might make an image larger, but not clearer."

"Magnification only causes images to get large but don't give any clarity."

"Without the brightness and resolution for a telescope you will see no image, making magnification useless because their would be nothing to magnify."

"Doesn't matter how big/close you can make something if you can't see it."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"I enjoy doing the in-class activities, I feel that it will help me to improve my learning."

"Can you go over the ellipses? I was super-confused."

"Could you go over retrograde and prograde motions?"

"What are key differences between Kepler's laws and Newton's laws."

"How does gravity pull things into an orbit so it actually moves around the planet and not fall right into it?"

"This section has been rough due to the different terminology. It's hard to remember specific definitions."

"Can you clarify more about telescopes?"

"Do you personally own a telescope? (No, because I use Cuesta College telescopes whenever I feel like it.)

Online reading assignment: images produced by lenses, thin lens equations, cameras and eyes

Physics 205B, spring semester 2020
Cuesta College, San Luis Obispo, CA

Students have a bi-weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on examples of images produced by lenses, thin lens equations and camera and eyes.


Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.

"Converging lenses cause light rays to converge toward a focal point, while diverging lenses cause light to diverge (spread out). Converging lenses can produce either real or virtual images, while diverging lenses can only produce virtual images. The thin lens and magnification equations help us determine the location, size, and nature of the image a lens produces."

"I understand the image tracings a little bit better. I understand how the height and what side of object the image is on effects the the orientation and size of the image. I also understand that if the lines can be traced back that makes the image virtual."

"When drawing ray tracings, rays move from left-to-right with the object located on the left of the lens. Once the tracing is complete, if it is a virtual image, then the image would be located on the left of the lens. If the image is real then the image will be located to the right of the lens."

"The magnification equation uses the ratio of image height to object height, or the negative value of image distance to object distance. Regardless of whether or not the image is enlarged or diminished, an upright image will always have a positive height value and an inverted image will have a negative height value."

"How the thin lens equation and magnification equation are derived. I understand the basics of the thin-lens and magnification formula. I understand how near point is corrected for someone who is farsighted and how the far point is corrected using a diverging lens for someone who is nearsighted."

"This section is still on converging and diverging lens, however, it talks about how cameras and eyes are similar because they are both converging lens which produce real images. Camera have a fixed focal length lens meaning on the image and object distance is the only thing influencing its equation. Eyes have fixed image length distance since the eye is constant. This means that only object distance and focal lens are then only factors that can change."

"The difference in the different 'sighted-nesses.' Myopia being nearsighted, meaning they can see things near to them better. Versus hyperopia being far-sighted meaning they can see things far to them better. I have heard of these terms before, but it is cool to know the physics behind it!"

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.

"Real and virtual images are still giving me a little but of trouble. I am always unsure on my answers. Also comparing ray tracings was oddly difficult."

"I'm still struggling to understand how to distinguish between real/virtual, upright/inverted, and enlarged/diminished images."

"I'm still confused about what kind of image is produced through each lens, whether the image is real, virtual. I'm also not sure how to apply the thin lens equation."

"I'm still having trouble with the distinction of real image versus virtual image. Diverging lens are always virtual I believe but need more refreshing of these concepts."

"I do not understand the sign conventions for lenses, drawing ray tracings might help. The sign conventions were just given as a list in the book so it's hard to relate them to images being formed."

"How to use the thin lens and magnification equations correctly in-relation to examples. Need some example problems and discussion to process this quantitatively to the best of my ability."

Identify the following thin lens parameters. (Only correct responses shown.)

Focal length: f [91%]
(Linear) magnification factor: m [89%]
Object distance: d_o [94%]
Object height: h_o [83%]
Image distance: d_i [86%]
Image height: h_i [94%]

For a simple camera, identify which parameter(s) must change or remain constant in order to focus on different distance objects.

Focal length: remains constant [49%]
Lens-to-film distance: changes [60%]

For a model eye, identify which parameter(s) must change or remain constant in order to focus on different distance objects.

Focal length: changes [80%]
Lens-to-retina distance: remains constant [74%]

Identify the type of lens, image, and example ray tracing produced in the online reading assignment examples. (Only correct responses shown.)

Lens: converging [66%] (Only converging lenses can make inverted images.)
Image: real [63%] (All inverted images are real.)
Ray tracing: 1 [46%]

Lens: diverging [43%] (Only diverging lenses can make upright, diminished images.)
Image: virtual [46%] (All upright images are virtual.)
Ray tracing: 6 [26%]

Lens: converging [60%] (Only converging lenses can make upright, enlarged images.)
Image: virtual [46%] (All upright images are virtual.)
Ray tracing: 4 [20%]

Lens: diverging [49%] (Only diverging lenses can make upright, diminished images.)
Image: virtual [49%] (All upright images are virtual.)
Ray tracing: 7, 8, 9 or 10 [31%]

Lens: converging [40%] (Only converging lenses can make inverted images.)
Image: real [40%] (All inverted images are real, as the candle is upright, and the projected image is upside-down.)
Ray tracing: 1 [11%]

Lens: diverging [51%] (Only diverging lenses can make upright, diminished images.)
Image: virtual [54%] (All upright images are virtual.)
Ray tracing: 7, 8, 9 or 10 [28%]

Lens: converging [60%] (Only converging lenses can make upright, enlarged images.)
Image: virtual [46%] (All upright images are virtual.)
Ray tracing: 5 [29%]

Lens: converging [54%] (Only converging lenses can make inverted images.)
Image: real [46%] (All inverted images are real, as the slide is upside-down, making the projected image on the wall upright.)
Ray tracing: 2 [26%]

A person with no vision defects can see both nearby and distance objects. Identify what can be seen by a person with the following vision defects. (Only correct responses shown.)

Myopia: can see nearby objects [97%]
Hyperopia: can see distant objects [97%]
Presbyopia: can see distant objects [91%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Can we please go over real and virtual images again in the examples above? I wasn't sure how to identify the ray tracings."

"I really just don't understand how we can tell whether an image is produced from a converging or diverging lens. So confused!"

"I feel that I need a lot of help with the lenses and real-life examples because I feel lost."

"Is the difference between concave and convex lenses the same as the difference between converging and diverging lenses?" (Yes, exactly.)

"I'm really unsure of how to distinguish between what produces a real or virtual image just based on the object. I feel like I missed a blog presentation that explained this because I've looked through them and I can't seem to find the best resource to help me understand them. I can see on the worksheet where the light rays intersect (or don't) if they are real or virtual and also if they are upright or diminished. I just don't know how we can determine this just be knowing what object light isis passing through. Maybe I am missing something really obvious?" (We officially didn't have a super-specific reading or lecture on this, but we had a flowchart to determine whether an image or real or virtual, and this process is something we'll pick up from practice rather than from strict formal definitions.)

"I thought this chapter was very intriguing because of its relation to human anatomy."

"Is it accurate to say that you can see a real image without having to look directly through a converging lens but in order to see a virtual image you have to look through the lens that produced it?" (Yes. You can only project a real image onto a screen, as you'll be doing in lab this week. You can see both real or virtual images by looking back through the lens.)

"Interesting material, also it's just been so cold in the mornings lately!"

Online reading assignment: lenses

Physics 205B, spring semester 2020
Cuesta College, San Luis Obispo, CA

Students have a bi-weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on lenses.


Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.

"A focal point is the point at which rays or waves meet after reflection or refraction and the distance between the focal point and the lens is the focal length."

"Converging lenses refract light to a focal point and that diverging lenses refract light away from a point in space. In certain cases the image produced can be diminished, enlarged, upright or inverted."

"The distance that an object is from a lens determines where it is shown. It may also be inverted based on the distance from the lens."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.

"I do not understand real vs virtual images. I think I have a small grasp on both terms but why one is considered real and the other not, confuses me. Also every one of my diverging lens rays is the same which cannot be right."

"I'm not sure when the image projected is diminished, enlarged, upright or inverted. I also am not sure how to draw ray tracings for when the object is in front of the secondary focal point."

"The parts that seem confusing are the principal rays for converging lens. As well as the principal rays for diverging lens. I definitely found the ray tracing worksheets confusing."

"I had trouble figuring out when an image would be enlarged or diminished."

"Could work on drawing better."

"Nothing confusing I just want more practice to solidify my understanding."

Complete the online reading assignment ray tracings as best as you can. Identify the type of image produced for each ray tracing. (Only correct responses shown.)

Converging lens 1: real image [65%]
Converging lens 2: real image [70%]
Converging lens 3: (no image produced) [46%]
Converging lens 4: virtual image [41%]
Converging lens 5: virtual image [46%]
Diverging lens 6: virtual image [38%]
Diverging lens 7: virtual image [38%]
Diverging lens 8: virtual image [35%]
Diverging lens 9: virtual image [38%]
Diverging lens 10: virtual image [38%]

Complete the online reading assignment ray tracings as best as you can. Identify the image orientation and size produced for each ray tracing. (Only correct responses shown.)

Converging lens 1: inverted, diminished [62%]
Converging lens 2: inverted, enlarged [54%]
Converging lens 3: (no image produced) [44%]
Converging lens 4: upright, enlarged [49%]
Converging lens 5: upright, enlarged [51%]
Diverging lens 6: upright, diminished [41%]
Diverging lens 7: upright, diminished [38%]
Diverging lens 8: upright, diminished [30%]
Diverging lens 9: upright, diminished [35%]
Diverging lens 10: upright, diminished [32%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"I need a lot of help understand real and virtual images. I do not understand how to tell the difference."

"May we review real/virtual images? I found that quite confusing."

"Can we please see each ray tracing in class so I know if I drew mine right?"

"I have questions about drawing the rays."

"More individual ray worksheets would be awesome!"

"I drew the rays but I'm still not sure what I'm looking at..."

"This is going to take some getting used to."

"Why can't diverging lenses create an image larger than the object?" (When a diverging lens makes an image from an object, the resulting image will always be smaller. However, if a diverging lens takes light that passed through another lens first (making it a virtual object, which we won't get into this semester, as those ray tracings are pretty intense), then the resulting image can be bigger than the original object!)

"Also out of curiosity how old is P-dog?" (I'm old. Old AF.)

Online reading assignment: history of astronomy, telescope powers (SLO campus)

Astronomy 210, fall semester 2019
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on reviewing the history of astronomy, Kepler's and Newton's laws, and telescope powers.


Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"That many of the original astronomers/scientists had very detailed ideas of how the universe worked simply from two assumptions: Earth is the center of motion, and everything was created in perfect patterns."

"It was interesting (and super-impressive) what some of the early astronomers were able to figure out and make good guesses, even if they were wrong, with equipment that only helped the unaided eye."

"The history of astronomy--the universe was too complex to be understood, but thanks to the contribution of earlier astronomers we have a better understanding of the solar system."

"I liked how a lot of the enlightenment thinkers were alive at the same time, interacted, supported or refuted each other's theories."

"The persecution of Galileo was decided on what was a technicality from a previous order years ago."

"That Galileo Galilei was sort of a pompous ass! It was funny to me that the textbook described him as 'outspoken, forceful, and sometimes tactless.' He offended a lot of people, including the pope."

"It's crazy to think that Galileo went on trial for his defense of Copernicus which resulted in a life of confinement, just because of the belief that God could make the universe in a way that 'appeared different to humans.'"

"I find it incredibly interesting that Galileo's middle finger is preserved. The irony behind his actions and how now he is an established figure of science, when back in his era the church tried to silence him for heresy is quite amusing."

"That Galileo was able to see the phases of Venus. I found this interesting because it closely related to the phases of the moon that we recently learned about."

"The difference between Kepler's laws and Newtons laws, since one is 'how' and the other 'why' planets move in our solar system."

"It's crazy to think that Earth revolves around the sun with an inconsistent speed."

"That planets move faster when closer to the sun and slower when farther away, because that's a completely new concept for me!"

"I liked the idea of Newton's cannon and that it is almost impossible to build. People should definitely build it."

"I really liked being able to grasp the concept of elliptical orbits and exactly how it happens. Newton's cannon along with the online simulation perfectly showed the progression and formation of an orbit."

"I think it's super cool that telescopes have so many parts to them, but it is also confusing."

"Telescopes are really cool. It's crazy that they can see so far and be so accurate. It reminds me of a time I went to santa margarita lake and there were a bunch of astronomers with HUGE telescopes set up and the detail was pretty mind blowing. Still don't know how they work completely though."

"I found it interesting that the magnifying power of a telescope doesn't matter as much as it's light-gathering power or its resolving power. It is interesting that it doesn't help you see more detail in general."

"The many components of a telescope, and why they need to be so large."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"Nothing in particular is confusing about the historical past of astronomy to me. It's just history."

"How did Kepler figure out the orbits of planets in extreme detail? I simply have no idea how he was able to such a thing."

"Trying to understand Kepler's laws; I can't wrap my head around the geometry of elliptical orbits."

"I was slightly confused when it came to Kepler's laws. They aren't as easy to understand for me compared to that of Newton's laws. I would like to go over Kepler's laws a little more to have them make more sense."

"I didn't find anything that was too confusing. But I would like a refresher on the differences between Kepler's laws and Newton's laws."

"In the book they state that objects orbiting Earth are falling towards Earth's center, and that because of its horizontal velocity the object orbits instead of runs into Earth. I have a hard time imagining how objects orbiting Earth are falling toward earths center but managing to stably orbit Earth without running into it. I understand that orbiting works because of the horizontal velocity but, I can't understand how objects are falling towards Earth's center while also orbiting."

"Telescopes have so many parts to them, so I did kinda get lost trying to understand what each one is for."

"I am having trouble understanding the parameters of a telescope. Specifically, I'm getting stuck at the primary focal length because I don't fully understand the difference between the different telescopes and which has a lens and/or mirror. "

"How light gathering power and resolving power are both dependent on the same component of a telescope, but not in the same way."

"I'm having a hard time understanding all the parts of the telescopes and what they do. I'm more of an auditory learner, so I think if we go over this in class I should be fine."

When a planet is undergoing retrograde motion, over several nights it moves __________ with respect to the background stars.

east to west.	************************* [25]
west to east.	******* [7]
(Either of the above choices is possible.)	[0]
(Unsure/lost/guessing/help!)	* [1]

When a planet is undergoing prograde motion, over several nights it moves __________ with respect to the background stars.

east to west.	******* [7]
west to east.	************************** [26]
(Either of the above choices is possible.)	[0]
(Unsure/lost/guessing/help!)	[0]

Categorize each of Kepler's laws.
(Only correct responses shown.)

Kepler's first law: describes the shape of a planet's orbit. [91%]
Kepler's second law: describes the speed of a planet along its orbit. [94%]
Kepler's third law: describes the speed of a planet along its orbit. [64%]

Categorize each of Newton's laws.
(Only correct responses shown.)

Newton's first law: relates forces with changes in motion. [61%]
Newton's second law: relates forces with changes in motion. [82%]
Newton's third law: describes a property of forces. [52%]

The __________ power of a telescope depends on the: (Only correct responses shown.)

light-gathering: diameter of the primary lens/mirror [70%]
resolving: diameter of the primary lens/mirror [67%]
magnifying: both the focal lengths of the primary lens/mirror and eyepiece: [30%]

The least important feature to consider when purchasing an optical telescope is the __________ of its images.

brightness.	***** [5]
resolution.	** [2]
magnification.	****************** [18]
(Two of the above choices.)	****** [6]
(Unsure/lost/guessing/help!)	** [2]

Briefly explain your answer for the least important feature to consider when purchasing an optical telescope.

"The least important feature to an optical telescope is its magnifying power. This is the ability to enlarge the image seen through the telescope. Light gathering power and detail are the most important when buying a telescope."

"The magnification is the least important feature of an optical telescope because the magnification can be changed by changing the eyepiece. The light-gathering power and resolving power of an optical telescope cannot be changed, and these properties affect the amount of detail that can be seen. A higher magnification does not necessarily show more detail."

"Well, reading the book it states that the magnifying power is the weakest part when considering to buy a telescope because the magnifying power doesn't necessarily show more detail when using it."

"Magnification is the least important feature. The most important thing is getting bright, clear images that you can enlarge after the fact."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"It was hard to find the difference between prograde and retrograde."

"I didn't know that the planets moved in retrograde! It makes more sense now why visible planets like Mars hang around the same spot in the sky for a while before prograding and moving further across the horizon."

"Are Kepler's laws and Newton's laws interconnected in any way?" (Definitely yes, and we'll make sure to make those connections in class tonight.)

"I would like to know more about how to choose a telescope."

"Do you own a telescope? And if you do, how often do you use it to look at the sky?" (No, because I get to use Cuesta College telescopes whenever I feel like it.)

"Could you talk more about light and telescopes in class please?"

Online reading assignment: history of astronomy, telescope powers (NC campus)

Astronomy 210, fall semester 2019
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on reviewing the history of astronomy, Kepler's and Newton's laws, and telescope powers.


Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"I found pretty interesting that although planets all orbit around the sun, they move at different paces and for different lengths of time. It's as if they're not just planets, but have their own purpose in the universe."

"I found reading about the ancient astronomers most interesting--history has always been an interest of mine and learning how astronomy relates to history has been fun."

"Kepler's three laws of planetary motion. The first law states that the orbit of the planets are ellipses with the sun at one focus. The second law talks about the distance between the sun and planet. The third talks about a planet's orbital period."

"I found Kepler's laws to be very interesting. The fact that there are all these different ways planets move was very interesting to me. Newton's laws were interesting too, but easier to understand, having learned about those laws in other science classes before."

"Newton's first law states what happens if there were no force--because I think it's crazy then how if something is moving it will continue to move, and if its stationary it will stay still."

"Newton's cannon. I thought it was interesting because that would be really cool if we could actually do an experiment like shown on the presentation."

"Newton's cannon--it looked really cool and I'm sure there's a lot of math and physics behind it but I really tried to understand what was going on."

"The telescope reading was interesting for me because of the different types of telescope there are, and how some work better then others."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"Retrograde motion overall kind of confuses me. Orbital mechanics are something I've never really had to think about other than in video games."

"Protograde and retrograde motion, it's just a weird subject to digest."

"I'll need a better breakdown of Kepler's laws."

"I am confused a bit on Kepler's second and third law. I kind of understand how the distance between the sun and planet affects the speed of said planet but I still need more explaining. Also a bit confused on the semi-major axis."

"The whole Newton's cannon thing. I understood the general gist of it, but perhaps a little more information in terms of the relation to Kepler's laws."

"The entire telescope presentation isn't confusing until it gets to light gathering power and area and so forth."

"The whole telescope presentation was very confusing to me. I feel like maybe it will make sense once I actually use one, but just reading about it confuses me a bit."

When a planet is undergoing retrograde motion, over several nights it moves __________ with respect to the background stars.

east to west.	********* [9]
west to east.	***** [5]
(Either of the above choices is possible.)	* [1]
(Unsure/lost/guessing/help!)	*** [3]

When a planet is undergoing prograde motion, over several nights it moves __________ with respect to the background stars.

east to west.	****** [6]
west to east.	******** [8]
(Either of the above choices is possible.)	* [1]
(Unsure/lost/guessing/help!)	*** [3]

Categorize each of Kepler's laws.
(Only correct responses shown.)

Kepler's first law: describes the shape of a planet's orbit. [72%]
Kepler's second law: describes the speed of a planet along its orbit. [89%]
Kepler's third law: describes the speed of a planet along its orbit. [50%]

Categorize each of Newton's laws.
(Only correct responses shown.)

Newton's first law: relates forces with changes in motion. [78%]
Newton's second law: relates forces with changes in motion. [72%]
Newton's third law: describes a property of forces. [67%]

The __________ power of a telescope depends on the: (Only correct responses shown.)

light-gathering: diameter of the primary lens/mirror [44%]
resolving: diameter of the primary lens/mirror [33%]
magnifying: both the focal lengths of the primary lens/mirror and eyepiece: [0%]

The least important feature to consider when purchasing an optical telescope is the __________ of its images.

brightness.	* [1]
resolution.	[0]
magnification.	************ [12]
(Two of the above choices.)	* [1]
(Unsure/lost/guessing/help!)	**** [4]

Briefly explain your answer for the least important feature to consider when purchasing an optical telescope.

"Magnification is the least important because light gathering power and resolving power are most important."

"I am not sure, I am guessing it is magnification because in order to see through a telescope the brightness of the object must be visible in order to study it?"

"You have to gather enough light first to capture the image before zooming in."

"It doesn't help to magnify it if it is still blurry."

"I'm not sure. They all seem kind of important."

"In the reading it says 'magnifying power can be changed simply by changing the eyepiece,' that's why I chose my answer."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Were others tried for their beliefs about the planets or just Galileo and if he was the only one then why?" (In the 16th century Giordano Bruno proposed stars could each have planets that could host life, and that the universe is infinite and has no center. Although technically he was tried and burned at the stake mainly for his unconventional religious beliefs, his radical ideas on cosmology certainly brought him a lot of undue attention.)

"Crazy to think how Newton thought of all these things."

"Can you just go over the slides a bit, This week's reading and slides were a little hard to understand, yet it was interesting."

"What is the importance of the different telescope features. I know the slides explain it just having a hard time to process it."

"I think it's cool how telescope work."

"What are we going to focus on more, optical telescopes or radio telescopes?" (Definitely optical telescopes, although light gathering power and resolving power in terms of the size of radio telescopes works similar to optical telescopes.)

"Can we please go over the last few questions based on the telescopes?"

"Why is it so important to measure a telescope's lens or mirror?" (Those measurements will tell you how powerful (or not) a telescope is at gathering light, resolving small details, and/or magnifying images. We'll practice measuring telescopes and comparing their powers on Thursday.)

"I'm just pretty confused on everything. I'm not sure what to ask just yet."