Go to this link and answer the questions below: http://webphysics.davidson.edu/p

Question

Go to this link and answer the questions below:

http://webphysics.davidson.edu/physlet_resources/dav_optics/examples/eye_demo.html

1. Read through the “normal vision” text below the simulation- follow the directions to view a far source using a healthy eye.

- Comment on how the light rays from a far source are organized.

-- Comment on how the light rays change direction when entering the eye

- Do you expect the eye to stimulate a converging or diverging lens by looking at these light rays? Explain

- Comment on whether or not you believe the image would be seen in focus for this healthy eye and why

2. Now clear, the far source lines by clicking again on the far source. Click on the near source and repeat a-d form #1 above.

3. Read the section called ‘Near Point and Far Point’ on the page.

- Follow the directions for following your own finger and provide an estimate of your near point distance.

- Describe what happens as you move the source closer to the healthy eye in the simulation

     -   Now, clear the simulation and choose a farsighted eye and a far source. How does the focal length change compared to a healthy eye? Describe how you need to change the slider to make the image focus on the farsighted retina.

- Repeat ( C) for a nearsighted eye. Is there a way to focus the image on this eye without glasses?

4. Read over the part titled “ corrective lenses” think about what types of images and the image locations for converging and diverging lenses focus – change the focal length for the eyeglass lens for both near and far – sighted eyes with the eyeglass such that a far source is focused on the retina. When found for each scenarios copy an image of the simulation into a doc file. Comment on how you were able to focus the images using what you know about converging and diverging lenses.

Explanation / Answer

Ans 1

(i) Light rays from a far source are parallel.

(ii) The light rays bend towards the eye when entering the eye.

(iii) The eye works as a converging lens.

(iv) When parallel beam enters a converging lens, image is formed at the focus. Hence it is expected that this

healthy eye will form image of the far source at its focus.

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