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Comments (11)
johnlittlephysics said
at 6:45 pm on Jan 11, 2014
iPad app for lens simulation!
Download "RayLab" (by Kamyar Ghandi) https://itunes.apple.com/sg//raylab/id710190065?mt=8
Tips:
1. Under Models, don't use existing ones; click "+" on top right menu to create new model
2. Click "+" on top right menu to select Biconvex Lens
3. Click icon for Options (top right menu and select the following
- object/image
- wavelengths: select 1
- wavelength1(nm): change 420 to 720 (red)
- source points: 1
- fan lines: 30
- drag slide bar (below fan lines) towards middle
4. Click on left curved surface of lens (becomes thick red line), click icon (top right menu) for Surface 1 properties and change R from 1.0000.. to 2.000...
5. Similarly click on right curved surface of lens and drag to make a nice Biconvex lens.
6. Move the lens to the origin of the scales.
johnlittlephysics said
at 6:54 pm on Jan 11, 2014
Sample of a lens diagram for object distance u > f the focal length of lens
Showing object, lens and real image (next to vertical screen)
https://www.dropbox.com/s/xzga5e09s7uyqou/Photo%2011-1-14%206%2024%2029%20pm.png
johnlittlephysics said
at 6:58 pm on Jan 11, 2014
Sample of a lens diagram for object distance u < f the lens focal length, showing virtual image on the left
https://www.dropbox.com/s/rox2takbg33l8sc/Photo%2011-1-14%206%2028%2020%20pm.png
A short-coming is it does not show the standard light rays and lines used in construction.
johnlittlephysics said
at 7:14 pm on Jan 18, 2014
Download the Lenses notes above. The front page shows syllabus. First assessment objective includes diverging lense (how rays diverge after passing it), but the rest are for converging (or convex) lenses. Same for all notes to download from iTunesU.
johnlittlephysics said
at 9:29 am on Jan 19, 2014
Mini-assignment for 2 marks (counted with pop quizzes):
Email me your own solution (typed or drawn) by Wed 22 Jan of the following problem:
Using the lens ray diagram at https://www.dropbox.com/s/dhf0yhiainnrpup/Photo%2019-1-14%209%2005%2030%20am.png
derive the lens formula.
Hints: magnification = v/u = hi/ho (ratio of heights of image to object) and consider gradients of similar triangles in the diagram.
johnlittlephysics said
at 10:54 pm on Jan 21, 2014
402 Cheryl and Yingting, and 405 Tessa and Kah Leng have submitted their solutions. Would share these here soon.
- Mr Ang
johnlittlephysics said
at 3:55 pm on Feb 16, 2014
Updates: refer to http://nyghsec3physics.pbworks.com/w/page/75157739/lens_formula
or Lens formula derivation under Physics Alive.
Tam Li June said
at 11:07 am on Jan 21, 2014
Hi Mr Ang,
Is it true that for counting magnification, for the v and u values that we use, we do not have to put any negative sign regardless whether the image is virtual or not?
Thank you.
johnlittlephysics said
at 2:28 pm on Jan 21, 2014
Yes, usually, we use magnification as a ratio of the sizes or heights, so no sign needed.
Tam Li June said
at 5:56 pm on Jan 23, 2014
Hi Mr Ang,
May I check how do we approach qns 8) of our lenses pop quiz?
Thanks
johnlittlephysics said
at 10:44 pm on Jan 23, 2014
Light rays reaching the lens are horizontal and parallel, so they would meet at the focal point of the lens (where the image is).
Hence distance from the lens to the image is the focal length f.
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