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.)
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