Author Topic: Thin Lens (converging/diverging lens/mirrors)  (Read 1152177 times)

Fu-Kwun Hwang

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Thin Lens (converging/diverging lens/mirrors)
« on: January 30, 2004, 12:02:28 am »
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Equation for thin lens: $frac{1}{p}+frac{1}{q}=frac{1}{f}$ where p is the distance between object and lens, q is the distance between image and lens, and f is the focus length of lens.
blue linestrace of light path
green linesbackward tracing for virtual image
small red linesdistances f and 2*f away from the center of lens.
1st textfieldcurrent mouse position (x , y) relative to lens
white vertical linereference line (you can click and drag it left/right)
yellow linelight path for paraxial ray assumption(mirror only)

Parameters can be changed :
  1. Select Lens for thin lens effect(default)

  2. select mirror for concave/convex mirror effect

  3. default: assume paraxial ray (you can turn it off)

  4. press toggle button +/- to change between converging/diverginglens

  5. Move the object

  6. click near tip of the object, and drag it to where you like it and release the mouse button.

  7. Move the lens/mirror:

  8. click near center of the lens, and drag it to left or right.

    if click with left mouse button, only lens will move.

    if click with right mouse button, object will move with lens.

  9. Change the focus length of the lens/mirror

  10. click near the top/bottom of the lens/mirrir, then drag the mouse . Try it!

  11. if you adjust the size of window, parameters reset to default values.

  12. you can open more then one window to compare different cases, close the created window to Quit. Pressto open another Lens window!

  13. you can change the following parameters inside the "textfield".

    You are welcomed to check out another related simulation :Relation 1/p+1/q=1/f and What will happened if part of the light path were blocked

    You are welcomed to check out a wonderful thin Len flash animation created by a teacher in Taiwan

    More advanced topic

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  • Guest
« Reply #1 on: January 30, 2004, 09:02:46 am »
Subject: Lenses
Date: Sun, 01 Feb 1998 17:08:13 -0600
From: John Eagle <>
I think this page is great.
I stumbled into it one night while trying to find some insight on a physics assignment that I had.
I've used it ever since to check my work.
Something that might be helpful to a great number of people
would be a java applet with thick lenses and or two lense systems. Just a thought.
Thank you for taking the time to publish such a page John Eagle

  • Guest
« Reply #2 on: January 30, 2004, 09:11:28 am »
Subject: Lens/mirror
Date: Fri, 03 Apr 1998 16:16:37 -0600
From: Kelly <>
Mr. Hwang, I want to say that your virtual lab was unbelievably helpful to me.
I attend the university of wisconsin-madison and I was having problems with optics concepts.
I went under the internet and searched under lens and mirrors and fell upon your lab.
I am very grateful. I was a little upset last night when I wanted to access the lens mirror applet,
because I couldn't find it.
I guess even the virtual labs have hours of availability.
I guess that's my only suggestion,
which isn't a very necessary one to attend to when most of us can access it during the day.
Thanks again, Chris

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« Reply #3 on: January 30, 2004, 11:58:55 am »

Subject: Wow!!!
Date: Sun, 03 May 1998 15:39:11 -0600
From: The Lahrs
I just figured out that the inverted image is not virtual but real,
so everything makes sense now.
Keep up the good work.
John C. Lahr

  • Guest
« Reply #4 on: January 30, 2004, 11:59:36 am »

Subject: Wow!!!
Date: Sun, 03 May 1998 12:47:55 -0600
From: The Lahrs
I love your thin lens page:
What a great use of Java!
I use Netscape, by the way, and the applet worked just fine and was very speedy.
I've been trying to figure out why a glass rod creates an inverted (about one axis) virtual image.
Do you have an applet for a thick lens, or just a ray diagram that would show this effect?
Is the code still available? The link was not working when I tried.
It would be interesting to develop something like this for seismic waves.
I'm a seismologist now, but my first love is physics,
which was my undergraduate major at Rensselaer Polytechnic Institute.
Thanks again for providing the world this great applet.
John C. Lahr
-- * John C. and Jan H. Lahr * *
914 10th Street * *
Golden, Colorado 80401 * *
(303) 215-9913 * * * * *

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« Reply #5 on: January 30, 2004, 12:33:55 pm »
Subject: Thin Lens Java applet
Date: Fri, 19 Feb 1999 18:00:24 +1100

I was looking at your applet for the thin lens and really liked it. I am new to applets and
often it is possible to download them so that you can use them off line but I couldn't
work out what to do to download your applet.

I am a secondary teacher and would really like to show it to my students. Would I be
able to get a copy of it please.


Pam Evans

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« Reply #6 on: January 30, 2004, 05:42:18 pm »
From: Rick Matthews <>
Organization: Wake Forest University
Subject: Great applet!

I just discovered your lens applet. It is a great tool for
helping students come to understand lenses and mirrors.

Unless you object, I would like to assign a problem to my
students based on this applet.

Rick Matthews
Department of Physics
Wake Forest University 336-758-5340 (Voice)
Winston-Salem, NC 27109-7507 336-758-6142 (FAX)

  • Guest
Thin lens
« Reply #7 on: May 25, 2004, 03:08:12 am »
This is an awesome lab for teaching ray diagrams and optics basics! Thanks a bunch!

  • Guest
« Reply #8 on: August 13, 2004, 05:14:50 pm »

  • Guest
« Reply #9 on: August 13, 2004, 05:29:52 pm »
:shock: :shock: :shock: :shock: :shock:

  • Guest
fuk off
« Reply #10 on: August 13, 2004, 09:08:45 pm »
sup dude, yo this Thin Lens Demostration stuff rock!! i really enjoied it!! ill write a song now, c ya!

"go go go go go Go shory it's your birthday you gonna party like it's your birthday" by 50 cent

um abraço pra galera do marista


  • Guest
« Reply #11 on: August 18, 2004, 10:01:05 pm »
:arrow: This is an [b:134dfe8f92]amazing[/b:134dfe8f92] site man! very interesting to study lens and mirrors!! :P Now i can figure out how does it work! ;) As soon as you have news i'll be back! Se ya!!!

  • Guest
Ohhh povo feio
« Reply #12 on: August 18, 2004, 10:07:28 pm »
[b:73495ba837] Hadson é lindo!!!!!![/b:73495ba837], mas Enzo é muito chato e muito burro!! Klebinho é pegador!!!!!!!! Saulo parece c Silvio Santos, mas se acha muito!!!!!!!! Seus feios!!!
Gabarito de Matematica:
  1- a)
  2- b)


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« Reply #13 on: February 24, 2005, 08:16:57 pm »
I have few stupid questions...

I see mainly converging lenses collecting rays to one poit (pix A) but do they work another direction? (pix B) any differet solutions/ something usefull to know? I know I could use image conduit but they don't have enought resolution for 2000-3000 pixel CCD-bar/21mm wide...or I'm wrong? :?: In pictures arrow shows direction of ray.


Another Q is about focusing. Is there difference in working of D ja C assebly pictures? Are they equal?


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  • general physics
« Reply #14 on: February 25, 2005, 03:28:10 am »
i am very glad to see the applets, i would like see more of them :D