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: 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.)

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: quiz02BTLn



Sections 30882, 30883 results

0- 6 :
7-12 :	*** [low = 9]
13-18 :	***************
19-24 :	************* [mean = 20.5 +/- 5.5]
25-30 :	********** [high = 29]

Online reading assignment: lenses

Physics 205B, spring semester 2019
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.

"Converging lenses bring parallel rays of light and bring them to a focus at a point in space. On the opposite end, diverging lenses take parallel rays of light and spread them out from a point in space. So for the two cases, light either goes to a point or away from a point."

"If the redirected rays of light actually intersect at a location in space, then a real image is generated. If the redirected rays of light do not actually intersect at a location in space, but merely move outwards from an extrapolated location, then a virtual image is generated."

"Lenses and image formation through lenses was the topic of this weeks reading assignment. A focal point occurs when rays near principle axis and parallel to it converge to a singlepoint. Focal length is the distance between the focal point and the lens. Converging lenses cause incident parallel rays to converge to a single point. Diverging lenses cause the rays to move away from each other."

"Regardless of the position of the object that a diverging lens will always produce a virtual image instead of a real one. I understood that the different positions of an object in a convergent lens can produce a real or virtual image that can very in size and postion (inverted or upright)."

"Pretty much the only thing that I understand from the reading and the presentation is how to draw the rays. I can figure out the whole drafting part of it, but everything else is a little confusing. I think I understand the difference between real and virtual images, but I am not very confident in my abilities to do that correctly."

"I really don't understand the lens stuff very well."

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 could use some extra practice on the graphical model of rays, it hasn't quite clicked yet. I haven't grasped the usefulness of drawing rays and making a graphical model out of converging/diverging lenses."

"I can understand ray tracing diagrams fairly well, however I do need to keep practicing to get more comfortable recognizing what is occurring."

"I am still in the process of learning how to distinguish the resulting image as upright/ inverted, enlarged/diminished and real/virtual and how to identify and the definitions."

"All the lenses stuff seems confusing to me. I'm not sure when things are enlarged or not and I'm not sure how to tell if an image will be real or virtual by looking at the line drawings."

A lot of this was confusing. I still don't really get the whole labeling part of the images (upright/inverted, enlarged/diminished). I am also kind of confused about how to find the convergence point or location of the object or whatever that is. Very confusing. Hopefully this will make more sense in class. :)"

"The linear magnification equation."

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 [63%]
Converging lens 2: real image [71%]
Converging lens 3: (no image produced) [29%]
Converging lens 4: virtual image [60%]
Converging lens 5: virtual image [43%]
Diverging lens 6: virtual image [54%]
Diverging lens 7: virtual image [51%]
Diverging lens 8: virtual image [46%]
Diverging lens 9: virtual image [54%]
Diverging lens 10: virtual image [49%]

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 [47%]
Converging lens 2: inverted, enlarged [37%]
Converging lens 3: (no image produced) [26%]
Converging lens 4: upright, enlarged [26%]
Converging lens 5: upright, enlarged [34%]
Diverging lens 6: upright, diminished [46%]
Diverging lens 7: upright, diminished [40%]
Diverging lens 8: upright, diminished [43%]
Diverging lens 9: upright, diminished [43%]
Diverging lens 10: upright, diminished [37%]

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

"Honestly I think all of those are wrong. I was having a hard time figuring out what the rays meant based on their orientation. *Confused*"

"Can we discuss what happens with a converging lens when an object is located on its focal point?"

"I don't think I quite know how to tell if the image is upright/inverted or diminished/enlarged."

"Do you think for this particular section that it might be best to extensively read your presentations and take more from them than the chapter in the book?" (At least for now, perhaps. Later, the textbook will go into more detail especially for corrective optics.)

"I am severely confused."

"I have no idea what's going on this worksheet."

"This is very confusing and I am looking forward to seeing how you make this make sense."

"I'm a bit confused on which ray tracings this reading assignment is referring to. Is that referring to the handout from class?" (Yes.)

Physics quiz archive: lenses, optical instruments

Physics 205B Quiz 2, spring semester 2018
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz02P0wR



Sections 30882, 30883 results

0- 6 :
7-12 :
13-18 :	************** [low = 14]
19-24 :	***************** [mean = 20.4 +/- 3.8]
25-30 :	*** [high = 30]

Online reading assignment: lenses

Physics 205B, spring semester 2018
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.

"How to do ray tracings, but not sure what they are illustrating."

"I learned how to trace the light rays through each type of lens. I didn't understand it in class where the third line was supposed to go but I got it now."

"I understand the basics of diverging lens ray diagrams. I feel like I can successfully start to attempt these problems."

"I get that converging lenses take parallel rays of light and bring them to a focus at a point in space whereas diverging lenses take parallel rays of light, de-focuses them, and projects them outward away from a point that, when traced, ends up being in FRONT of the lens. The points (F) are FOCAL points. A real image occurs when rays of light intersect at a point in space (converging lenses). A virtual image occurs when rays do NOT intersect and move outward from an extrapolated location."

"Converging lenses causes incident parallel rays to converge at the focal point. Diverging lens causes incident parallel rays to diverge after exiting the lens. Diverging lens always forms a virtual image that is on the same side of the lens as the object and is upright and smaller relative to the object."

"A diverging lens will create a virtual image that is upright and smaller that the original."

"Lenses create images by refracting light through the lenses surfaces. Two different kinds of lenses manipulate light by either focusing beams or 'defocusing' beams of light to create an image."

"I understand that if the redirected rays of light intersect at a location beyond the lens, then the object is portraying a real image. I also understand if there is a lack of intersection beyond the lens among the redirected light rays then the image is a virtual image."

"I understand that I will have to study physics more than I am right now."

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 keep reading the presentation over and over again but can't figure out what the difference between real and virtual."

"I have go through it thoroughly yet but it is difficult to understand the way to draw a graph to find the image for a diverging lens."

"I found the ray diagrams to be a bit confusing at first but it is making much more sense now."

"I'm not quite sure when drawing ray diagrams whether a virtual or real image occurs. Are virtual images before the lens and real images after the lens? Some quick clarification would go a long way."

"I am still a little bit confused on virtual images vs real images. I'm not sure which is considered virtual or real when looking at the examples that we have on the reading assignment."

"Whether an image is real/virtual, upright/inverted, or enlarged/diminished was very confusing. The book and presentations weren't super helpful, perhaps I missed something!"

"I found converging lenses more confusing. I feel like they are much different from diverging lenses and would appreciate an introduction to these."

"I'm really confused on what a real and virtual image is. I see the definitions but I do not understand what they mean or look like."

"When is an image real or virtual? How do we determine image orientation? Those are the most confusing parts for me."

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 [55%]
Converging lens 2: real image [48%]
Converging lens 3: (no image produced) [35%]
Converging lens 4: virtual image [48%]
Converging lens 5: virtual image [42%]
Diverging lens 6: virtual image [48%]
Diverging lens 7: virtual image [39%]
Diverging lens 8: virtual image [32%]
Diverging lens 9: virtual image [45%]
Diverging lens 10: virtual image [45%]

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 [26%]
Converging lens 2: inverted, enlarged [32%]
Converging lens 3: (no image produced) [37%]
Converging lens 4: upright, enlarged [26%]
Converging lens 5: upright, enlarged [26%]
Diverging lens 6: upright, diminished [35%]
Diverging lens 7: upright, diminished [32%]
Diverging lens 8: upright, diminished [30%]
Diverging lens 9: upright, diminished [35%]
Diverging lens 10: upright, diminished [30%]

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

"This is beyond me right now, I will definitely need extra help. But hopefully I'm not alone!" (You are not alone.)

"I have absolutely no idea how to distinguish between upright/inverted or diminished/enlarged images for divergent or convergent lenses. Hopefully we will go over that in class." (We certainly will.)

"I would like to know what type of lens eyeglasses are made of. So would all eyeglasses have to be a form of converging lens or diverging lens? (Yes, depending on whether you needed glasses to see near, or to see far. We'll discuss this more next week, and even find out how to calculate a prescription for glasses, without having to go to four years of optometry school.)

Physics quiz archive: lenses, optical instruments

Physics 205B Quiz 2, spring semester 2017
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz02J4sZ



Sections 30882, 30883 results

0- 6 :
7-12 :	**** [low = 9]
13-18 :	********
19-24 :	********** [mean = 20.2 +/- 6.6]
25-30 :	******** [high = 30]

Online reading assignment: lenses

Physics 205B, spring semester 2017
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 converging lens will take parallel rays of light and bring them to a focus at a point in space and a diverging lens will take parallel rays of light and 'defocus' them away from a point in space. The focal point of a lens is the location where parallel light is brought to a focus."

"I saw the tutor and now I understand everything perfectly."

"How to draw out the principal rays, but that was about 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.

"I understand the different types of lenses but am having a tough time drawing them out. Once you go through certain parts of the lens, I am unsure how you determine what kind of ray it is."

"The diverging lens ray tracings on the worksheet were not as intuitive as I thought. Some clarification is definitely needed."

"Real vs. virtual images is confusing. A worked-out example of this would be helpful to explain the intersection of rays of light."

"Still unsure how the focal points work for a diverging lens."

"I am really confused on how to tell if something is classified as a real/virtual image and if it is upright/inverted and/or if it is enlarged/diminished. For example is there something that we should look for so that we can tell if an object is upright and enlarged? If the lines intersect on the left-hand side of the lens does that mean it is a virtual image (for both converging and diverging)? I would like more details on how to properly categorize these things."

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 [72%]
Converging lens 2: real image [76%]
Converging lens 3: (no image produced) [44%]
Converging lens 4: virtual image [56%]
Converging lens 5: virtual image [56%]
Diverging lens 6: virtual image [60%]
Diverging lens 7: virtual image [60%]
Diverging lens 8: virtual image [60%]
Diverging lens 9: virtual image [48%]
Diverging lens 10: virtual image [44%]

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 [36%]
Converging lens 2: inverted, enlarged [32%]
Converging lens 3: (no image produced) [20%]
Converging lens 4: upright, enlarged [12%]
Converging lens 5: upright, enlarged [20%]
Diverging lens 6: upright, diminished [24%]
Diverging lens 7: upright, diminished [20%]
Diverging lens 8: upright, diminished [25%]
Diverging lens 9: upright, diminished [20%]
Diverging lens 10: upright, diminished [24%]

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

"This got me as confused as a sea turtle on roller skates."

"I understood how to draw the lines, but not why or what I was doing."

"Can we go over the ray tracing worksheet questions?"

"Please focus more on real/virtual images."

"Let's go over how to identify if something is enlarged/diminished or upright/inverted."

Physics quiz archive: lenses, optical instruments

Physics 205B Quiz 2, spring semester 2016
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz02f3MA


Sections 30882, 30883 results

0- 6 :
7-12 :	* [low = 11]
13-18 :	*******
19-24 :	********************* [mean = 23.0 +/- 4.6]
25-30 :	************ [high = 30]

Online reading assignment: lenses

Physics 205B, spring semester 2016
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 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.

"Converging lenses focus parallel rays of light onto a central focal point, where diverging lenses spread parallel rays of light outward, or 'un-focus' them."

"Virtual images are images that are formed in locations where light does not actually reach. Light does not actually pass through the location on the other side of the mirror; it only appears to an observer as though the light is coming from this location."

"Converging lenses bring light waves into one focus point. Diverging lenses scatter light waves in outward directions. Diverging lenses produce virtual images, but some converging lenses can produce virtual lenses as well, given specific focal points and object distances."

"In a case-by-case approach, I am confident in my ability to recognize when images are real/virtual, upright/inverted, enlarged/diminished, or non-existent."

"How to connect the ray tracing lines but that is mostly 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.

"I found the concept of virtual images a little bit confusing. I also found it confusing how to determine the size and orientation of an image through a lens."

"Most of this."

"I am unsure what the ray going towards the 'secondary F' does to the image with a diverging lens. If a virtual image is produced when the ray going from the source to the center of the diverging lens intersects with the ray going away from the 'primary F,' then the 'secondary F' ray seems to have no purpose."

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 [77%]
Converging lens 2: real image [77%]
Converging lens 3: (no image produced) [44%]
Converging lens 4: virtual image [54%]
Converging lens 5: virtual image [46%]
Diverging lens 6: virtual image [46%]
Diverging lens 7: virtual image [44%]
Diverging lens 8: virtual image [36%]
Diverging lens 9: virtual image [46%]
Diverging lens 10: virtual image [44%]

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 [38%]
Converging lens 2: inverted, enlarged [38%]
Converging lens 3: (no image produced) [47%]
Converging lens 4: upright, enlarged [28%]
Converging lens 5: upright, enlarged [33%]
Diverging lens 6: upright, diminished [31%]
Diverging lens 7: upright, diminished [28%]
Diverging lens 8: upright, diminished [37%]
Diverging lens 9: upright, diminished [36%]
Diverging lens 10: upright, diminished [26%]

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

"Could you go over more of the ray tracings, that would help a lot!"

"That ray tracing worksheet made me want to crawl under my desk and cry :'("

"On the ray tracings, do you only need two lines intersecting to produce an image?" (Yes, two lines (if drawn correctly) is sufficient to locate the image, but having all three rays intersecting at the same location is good practice.)

"I'm not sure how an image is either diminished or enlarged."

"What is the difference between a real and a virtual image in the ray tracings? How do I know which is which?"

"Having a hard time visualizing what is the object is and how it is seen through the lens. More specifically I can't visualize clearly yet what my eyes would be looking at. Are my eyes on the left or right side of the drawing? Just confused at this point." (By convention light is traveling from left-to-right, so your eyes would be located on the right side, looking to the left of the page, intercepting these left-to-right traveling rays.)

Physics quiz archive: lenses, optical instruments

Physics 205B Quiz 2, spring semester 2015
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz02r0cK



Sections 30882, 30883 results

0- 6 :
7-12 :	******* [low = 9]
13-18 :	*************
19-24 :	****************** [mean = 19.9 +/- 5.7]
25-30 :	************** [high = 30]

Physics quiz question: angular magnification of a microscope

Physics 205B Quiz 2, spring semester 2011
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e Problem 24.37

A microscope has an objective lens and an eyepiece with focal lengths of +1.10 cm and +1.20 cm, respectively. The "barrel length" (distance between the lenses) of the microscope is 14 cm. The angular magnification of this microscope is:
(A) –240×.
(B) –19×.
(C) –11×.
(D) –8.3×.

Correct answer (highlight to unhide): (A)

The angular magnification M of a microscope is given by:

M = –(L – f_e)·N/(f_o·f_e),

where L is the distance between the objective and eyepiece, N = 25 cm is the nominal value for the near point, and f_o and f_e are the focal points of the objective and eyepiece, respectively. Thus with the given values given in the statement of the problem, the angular magnification can be calculated directly:

M = –((14 cm – (+1.20 cm))·(25 cm))/((+1.10 cm)·(+1.20 cm)) = –242.42424242...,

or to two significant figures, the angular magnification of this microscope is –240×, where the negative sign denotes an upside-down image viewed through the microscope.

(Response (B) is –N/(f_o·f_e); response (C) is –L/(f_o·f_e); response (D) is –(N – L)/(f_o·f_e).)

Section 30882
Exam code: quiz02wR4y
(A) : 6 students
(B) : 1 student
(C) : 1 student
(D) : 0 students

Success level: 75%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.67

Online reading assignment: lenses

Physics 205B, spring semester 2015
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 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.

"The principal rays and how to draw them. I also understand how to find out if the object is upright/inverted, enlarged/diminished and real/virtual."

"There are two types of lenses, converging lenses, and diverging lenses. Converging lenses will take parallel rays of light and bring them to a focus at a point in space. Diverging lenses will take parallel rays of light and defocus them away from a point in space."

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 am not sure what generates a real or virtual image and when it is upright or enlarged."

"The ray tracings, and am hoping that you would be able to go over them in class. The tracings do not make sense to me at all and I have no idea how to draw them or let alone name any of them."

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 [90%]
Converging lens 2: real image [83%]
Converging lens 3: (no image produced) [57%]
Converging lens 4: virtual image [52%]
Converging lens 5: virtual image [50%]
Diverging lens 6: virtual image [63%]
Diverging lens 7: virtual image [78%]
Diverging lens 8: virtual image [71%]
Diverging lens 9: virtual image [78%]
Diverging lens 10: virtual image [68%]

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 [55%]
Converging lens 2: inverted, enlarged [45%]
Converging lens 3: (no image produced) [59%]
Converging lens 4: upright, enlarged [49%]
Converging lens 5: upright, enlarged [34%]
Diverging lens 6: upright, diminished [58%]
Diverging lens 7: upright, diminished [57%]
Diverging lens 8: upright, diminished [48%]
Diverging lens 9: upright, diminished [50%]
Diverging lens 10: upright, diminished [43%]

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

"How do you know if an image is enlarged or diminished compared to the object on a ray tracing?" (With a ruler. ALWAYS USE A RULER.)

"Do diverging lens always create upright, diminished virtual images?" (Yes, for any object placed in front of it. That is one of the key patterns to these ray tracing examples.)

"It seems like since the objects on the right side are the intersection of actual rays, they are real; but the images on the left are from extrapolated rays, so they are virtual? Is that correct?" (Yes, you've found another one of the ray tracing patterns.)

"I am not comfortable with figuring out if an image is virtual or real. The same goes for knowing exactly when an object is appears upside-down or not? Could there be a combination of where half the image is right side up and the other half is upside down?" (No. An image must be a complete, whole version of the object, so it must be entirely upright or inverted.)

"Drawing the rays is confusing! How do you tell if an image is real or virtual? I hope we go over magnification and inversion because I'm really confused." (I will do my best to get you unconfused. This stuff isn't really that hard.)

"I wanted to put the freaked-out guy for these questions but there was no option." (Here you go: ≡:o .)

Physics quiz archive: lenses, optical instruments

Physics 205B Quiz 2, spring semester 2014
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz02O8Jt



Sections 30882, 30883 results

0- 6 :
7-12 :	*** [low = 11]
13-18 :	******
19-24 :	***************** [mean = 22.0 +/- 5.2]
25-30 :	************** [high = 30]

Online reading assignment: lenses

Physics 205B, spring semester 2014
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 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.

"I understand that converging lens refract light inward and are thickest at the center. Diverging lens bend light outward from the focal point and are thinnest at the center."

"An image is considered to be real when the light rays of a certain point on a certain object converge to a corresponding point on a certain image. It is considered virtual if light rays from a particular point appear as if they are diverged from that particular on that particular image, even though they actually didn't. I get that stuff."

"I understand the difference between a converging lens and a diverging lens. A converging lens takes parallel rays of light and makes them meet at a specific point in space. Diverging lenses do the opposite; they take parallel rays of light and spread them out at the focal point."

"Images are formed by reflection from mirrors and refraction from lenses. Lenses can be diverging or converging, meaning they 'focus' light or 'defocus' light, respectively. I can draw the two (or three) principal rays through a 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.

"Not sure what upright/inverted or enlarged/diminished means."

"I have no idea how to draw the principal rays. I thought I understood, but then I looked at the key for the ray tracing homework and now I'm completely lost, I don't know how I'm supposed to know which line goes where and at what angle. I'm even more lost on how to identify the type of image produced for ray tracings and identifying the orientation and size of the image."

"I am having a hard time distinguishing between a real and a virtual image. I somewhat understand the mirror example, but I would not know how to apply these concepts to lenses. Can we please go over more examples?"

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 [83%]
Converging lens 2: real image [69%]
Converging lens 3: (no image produced) [49%]
Converging lens 4: virtual image [57%]
Converging lens 5: virtual image [57%]
Diverging lens 6: virtual image [69%]
Diverging lens 7: virtual image [69%]
Diverging lens 8: virtual image [71%]
Diverging lens 9: virtual image [63%]
Diverging lens 10: virtual image [49%]

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 [46%]
Converging lens 2: inverted, enlarged [34%]
Converging lens 3: (no image produced) [46%]
Converging lens 4: upright, enlarged [26%]
Converging lens 5: upright, enlarged [29%]
Diverging lens 6: upright, diminished [34%]
Diverging lens 7: upright, diminished [34%]
Diverging lens 8: upright, diminished [35%]
Diverging lens 9: upright, diminished [46%]
Diverging lens 10: upright, diminished [26%]

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

"Two antennae got married, the ceremony was only so-so, but the reception was fantastic."

"I am so completely lost. The book was incredibly confusing and I so I was hoping the blog presentation would help, and it did a little, but I still have no idea how to do the ray tracing homework."

"The ray tracing worksheet was very confusing for me, could you go over it?" (Yes.)

"Isn't divergent lens 10 image the same size as the object?" (Very nearly so--it's just a little smaller than the object.)

Physics quiz archive: lenses, optical instruments

Physics 205B Quiz 2, spring semester 2013
Cuesta College, San Luis Obispo, CA
Section 30882, version 1
Exam code: quiz02hYp0



Section 30882 results

0- 6 :
7-12 :	* [low = 12]
13-18 :	************
19-24 :	************* [mean = 20.5 +/- 4.9]
25-30 :	******* [high = 30]

Online reading assignment: lenses

Physics 205B, spring semester 2013
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 using ray tracings to determine the images produced by lenses.

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 fact that there can be real and virtual images."

"The insanely adorable kitten playing in front of the mirror. It makes me want to get a cat."
(That was actually a polydactyl (extra-toed) kitten.)

"Learning about lenses is interesting because many people, including myself, wear glasses and we can see why we need the types of lenses that we do."

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

"Ray tracing is more confusing than it looks. There seem to be quite a few rules that need to be memorized to determine how a ray will be transmitted through a lens."

"The whole virtual image thing confuses me in reference to lenses."

"I get confused about determining which lenses are convex and which ones are concave!" (Concave lenses are thin in the center, thick on the edges--imagine each side looks like a cave: )(. Convex lenses are thick in the middle, thin on the edges--each side bulges out: ().)

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

"What is your favorite physics topic?" (Using x-rays to make holograms of atoms and atomic structures..)

"How do they make holograms like Tupac at the Coachella Music Festival?" (No actual holography was involved, merely a virtual image produced by partially reflective mirrors.)

Picto-quiz: lenses and images

Let's apply the concepts introduced in a previous presentation, where we used ray tracings to find images produced by converging and diverging lenses.

Pair up in groups of two or three, pick up a whiteboard, and for each of these real-world examples, decide whether this is a converging or diverging lens, producing a real or virtual image, and choose the corresponding ray tracing diagram (or diagrams) from your worksheet.

For this image produced by a water glass, is this produced by a converging or diverging lens? Is this a real or virtual image? Which ray tracing(s) ((1)-(10)) best match(es) this?

How do you know this?

For this image produced by a camera lens attachment, is this produced by a converging or diverging lens? Is this a real or virtual image? Which ray tracing(s) ((1)-(10)) best match(es) this?

How do you know this?

For this image produced by magnifying glass, is this produced by a converging or diverging lens? Is this a real or virtual image? Which ray tracing(s) ((1)-(10)) best match(es) this?

How do you know this?

For this image produced by a pair of glasses, is this produced by a converging or diverging lens? Is this a real or virtual image? Which ray tracing(s) ((1)-(10)) best match(es) this?

How do you know this?

For this image on a frosted glass screen produced by a lens on an optical bench, is this produced by a converging or diverging lens? Is this a real or virtual image? Which ray tracing(s) ((1)-(10)) best match(es) this?

How do you know this?

For this image produced by a door peephole, is this produced by a converging or diverging lens? Is this a real or virtual image? Which ray tracing(s) ((1)-(10)) best match(es) this?

How do you know this?

For this image produced by a glass paperweight, is this produced by a converging or diverging lens? Is this a real or virtual image? Which ray tracing(s) ((1)-(10)) best match(es) this?

How do you know this?

For this image produced by a slide projector, is this produced by a converging or diverging lens? Is this a real or virtual image? Which ray tracing(s) ((1)-(10)) best match(es) this?

How do you know this?