Dear Prof Hwang,

My friend in school wishes for an EJS applet that can allow inquiry into the working of a human eye (simple think converging lens) with another thin converging/diverging lens in front of the human eye.
from http://webphysics.davidson.edu/physlet_resources/dav_optics/Examples/eye_demo.html by Melissa Dancy and Wolfgang Christian
The applet is a simplified model of the eye in which the front of the eye is a single converging lens.

i tried to design one from your original applet but the codes is really beyond my ability.

would you be releasing a physics simulation for me and my friend to work on?

this are the objectives

1) To show that human eye lens is of variable focal length. We need to stretch/compress our eye to see far/near object
2) People with short sighted have a upper limit to their focal length
3) People with far sighted have a lower limit to their focal length
4) Old people can have both upper/lower limit to their focal length and hence need bifocal lens

thanks!

this is the original email from my friend

[quote]Hi Bro,

I was trying to show how our eyes work and was using your applet:
http://weelookang.blogspot.sg/2010/06/ejs-open-source-converging-diverging.html

I'm trying to make it a virtual lab to reinforce their learning.

Would it be possible to make the following changes?
[s]1) Full screen capability like Fu-kwun with more space for image/object: Too little room to show image/object (always out of screen; and unable to show object/image at "infinity")
(I saw your auto function but would much prefer a fixed screen for ease of comparison)
2) Default uncheck blue line (with option to check it): In practice, we only draw 2 lines to determine the image. 3rd line is merely for checking answer.
3) Option to add in "eyeball with retina" in background?
4) Disable –ve f (since eye cannot be –ve f and its not in syllabus)[/s]

Additional Objective besides the usual:
1) To show that human eye lens is of variable focal length. We need to stretch/compress our eye to see far/near object
2) People with short sighted have a upper limit to their focal length
3) People with far sighted have a lower limit to their focal length
4) Old people can have both upper/lower limit to their focal length and hence need bifocal lens

Thanks,
TK
[/quote]

i came up with this story board for ease of understanding the what the applet can do.

for 1:
normal eye focus
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=2507.0;attach=4874;image[/img]

normal eye with near object, but eye len can adjust to focus
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=2507.0;attach=4876;image[/img]

normal eye dont near glass, not focus
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=2507.0;attach=4878;image[/img]

for 2:

near sighted eye not focus
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=2507.0;attach=4880;image[/img]

near sighted eye  focus with help of a concave len
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=2507.0;attach=4882;image[/img]

for 3:

far sighted eye not focus
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=2507.0;attach=4886;image[/img]

far sighted eye  focus with help a convex len with far object
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=2507.0;attach=4888;image[/img]

far sighted eye  focus with help a convex len with near object
[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=2507.0;attach=4890;image[/img]

thanks!!