Online reading assignment: thin lens equations, cameras and eyes

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 thin lens equations and camera and eyes.

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 now understand how my contact lenses work. I had heard that vision degrades less with contact lens wearers than with eyeglass wearers, and I suppose that the non-existent distance between lens and eye is the cause."

"The comparative description between camera lenses and eyes--how in a camera the focal length is constant and in an eye lens the image distance is constant."

"That linear magnification is the defined as the (negative) ratio of the image height compared to the object height, and how that if m is positive the image is upright and negative shows up inverted."

"Vision defects was interesting to me because it described what visual defects I have that affect my ability to see objects at a distance (myopia)."

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

"Four years of post-graduate optometry school was condensed into a short presentation. Why does optometry school take so long?"

"I found it pretty clear the concepts that the thin lens and magnification equations were describing but am confused on how to use them. They seem pretty easy to plug-and-chug, but they don't seem intuitive. When or why are they positive or negative?"

"Drawing of the ray tracings was somewhat confusing, but I just need to spend more time doing it."

"I don't understand what a virtual image is."

"Determining if something is enlarged or diminished."

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

"I understand the basics of this but I'm lost on most of it. However, I got it enough to do the homework--that's good, right?" (Uh, yes.)

"Can you go over the difference between the virtual and real images again, I'm confused from these ray diagrams of where we are viewing the object from. Also please show us examples with the thin lens equations." (Sure.)