NTNUJAVA Virtual Physics Laboratory
Enjoy the fun of physics with simulations!
Backup site http://enjoy.phy.ntnu.edu.tw/ntnujava/
September 24, 2020, 12:05:18 am *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with username, password and session length
   Home   Help Search Login Register  
Know the universe as yourself and you can live anywhere in comfort. ...Lao Tzu (570-490 BC)
Google Bookmarks Yahoo My Web MSN Live Netscape Del.icio.us FURL Stumble Upon Delirious Ask FaceBook

Pages: [1]   Go Down
Author Topic: Ejs Open Source Two Lens Java Applet  (Read 14475 times)
0 Members and 1 Guest are viewing this topic. Click to toggle author information(expand message area).
Hero Member
Offline Offline

Posts: 1796


Embed this message
on: July 18, 2012, 04:52:44 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

Ejs Open Source Two Lens Java Applet by fu-Kwun Hwang, remixed by lookang

trying to make on for http://webphysics.davidson.edu/physlet_resources/dav_optics/Examples/eye_demo.html

Embed a running copy of this simulation

Embed a running copy link(show simulation in a popuped window)
Full screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop. This work is licensed under a Creative Commons Attribution 2.5 Taiwan License
  • Please feel free to post your ideas about how to use the simulation for better teaching and learning.
  • Post questions to be asked to help students to think, to explore.
  • Upload worksheets as attached files to share with more users.
Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!

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.

Normal Vision

Initialize a healthy eye by clicking on the link at the bottom of the applet. Then add a far source of light using the link at the top of the applet. Notice how the parallel rays of light from the far away source converge at the back of the eye on the retina. The retina is to the eye what film is to a camera. The retina is made up of nerves that convert the light energy into an electrical signal that is sent to the brain. So in order for an object to be "seen" its image must be FOCUSED on the back of the retina.


Now remove the far source and add a near source. Notice that the light from the near by source is focused behind the retina. In this case the person would see a blurry image. As evolution would have it, our eyes have the ability to accommodate. You can change the focal length of your eye by using the muscles of your eye to change the curvature of the lens. Try looking at a far away object and then at something close by, such as your finger. You will feel the muscles in your eye respond as you change your focus. In the applet accommodation is accomplished by using the slider at the bottom to vary the focal length of the lens. Vary the focal length of the lens, using the slider, until the image of the light source is focused on the retina.

Viewing Far Away Objects

People with normal vision focus on far away objects with their eyes relaxed. Notice that the far source in the applet was focused when the focal length was at its maximum, 1 unit. As you use your muscles to accommodate you shorten the focal length of your eye.

Near Point and Far Point

Put your finger in front of your eyes about an arm's length away. You should be able to see a clear image of your finger. Now slowly bring your finger toward you. At some point, you will no longer be able to focus on your finger and it will become blurry. This is your near point. It is the closest distance at which you can focus on an object. If you have not already done so, initialize a healthy eye with a near source of light focused on the retina. Now move the source of light toward the eye. At some point you will no longer be able to accommodate (using the slider) to focus the source. That is the near point for the eye in the applet. Notice that the eye in the applet is not to scale relative to a real eye. If we had made it to scale you would need a MUCH wider computer screen.

The far point is just like the near point except it is the furthest point an eye can focus on. For people with normal vision, the far point is at infinity.

Nearsightedness and Farsightedness

Initialize a nearsighted eye and add a far source. Notice that the light does not focus on the retina when the eye is relaxed. Instead, it focuses in front of the retina. Use the slider to try and focus the light. Notice that accommodation does not help in this situation. Now remove the far source and add a near source. Notice that the nearsighted person has no trouble focusing on the near by source. A person who is nearsighted can clearly see near objects but not far away objects.

Now initialize a farsighted eye and investigate it as you did with the nearsighted eye. Notice that a farsighted person can see far away objects but has difficulty focusing on near by objects.

Corrective Lenses

Initialize a nearsighted eye with a far source. Unaided, this eye can not focus on the far source. Now add an eyeglass lens. Notice that you can change the focal length (power) of the eyeglass lens by clicking on it and then dragging on the hotspots. You can make the lens either converging or diverging.

Since light is focused in front of the retina in a nearsighted eye, nearsightedness is corrected using a diverging lens. Can you find the correct focal length to correct this eye? In the same way, farsightedness is corrected using a converging lens.


Illustration by Melissa Dancy and Wolfgang Christian

*** There are 1 more attached files. You need to login to acces it!
« Last Edit: July 24, 2012, 09:03:14 pm by lookang » Logged
Pages: [1]   Go Up
Know the universe as yourself and you can live anywhere in comfort. ...Lao Tzu (570-490 BC)
Jump to:  

Related Topics
Subject Started by Replies Views Last post
Physlets Optics java applet: A simple object on the left of the lens and a lens
Collaborative Community of EJS
lookang 0 9459 Last post September 02, 2008, 01:47:38 pm
by lookang
Ejs open source converging & diverging Lens object image high school java applet
Collaborative Community of EJS
lookang 19 62395 Last post October 01, 2012, 02:38:56 pm
by lookang
Ejs Open Source Geostationary Satellite around Earth Java Applet
Collaborative Community of EJS
lookang 18 43508 Last post April 18, 2013, 01:48:33 pm
by lookang
Ejs Open Source Rolling Solid & Hollow Sphere with Slipping java applet
Collaborative Community of EJS
lookang 5 12403 Last post March 22, 2018, 12:18:22 pm
by lookang
Ejs Open Source Young's Double Slit Java Applet
Collaborative Community of EJS
lookang 1 11168 Last post June 25, 2013, 11:01:27 pm
by lookang
Powered by MySQL Powered by PHP Powered by SMF 1.1.13 | SMF © 2006-2011, Simple Machines LLC Valid XHTML 1.0! Valid CSS!
Page created in 0.117 seconds with 24 queries.since 2011/06/15