Download Problem Set 7: Optical Phenomena

Problem Set 7: Optical Phenomena
1. What is the difference between polarized and unpolarized light?
1. Unpolarized light with intensity Io falls on a Polaroid sheet, the transmitted intensity is what fraction of
the original intensity? 50%
2. Two polarizing filters are placed in the path of a beam of light. The analyzer is then rotated until the
intensity is at a maximum. What is the relative orientation of the transmission axes of the filters when
maximum intensity is transmitted? Parallel (50%) What is the relative orientation of the
transmission axes of the filters when minimum intensity is transmitted? Perpendicular (0%)
3. What produces iridescence? Thin film interference
4. What causes the spectrum of colors seen in gasoline splotches on a wet street? Why are these not seen
on a dry street? Thin film interference. There is no difference in distance traveled by
the waves and therefore no interference between waves to produce the colors.
5. What phenomenon distinguishes longitudinal waves from transverse waves? polarization
6. Why will light pass through a pair of Polaroids when the axes are aligned but not when the axes are at
right angles to each other? When aligned, one of the 2 dimensions of the wave can fit
through both “gates” or filters. When perpendicular, one filter takes out one
dimension while the other filter removes the other dimension.
2. Why is light from a common lamp or from a candle flame nonpolarized?
3. In what direction is the polarization of the glare that reflects from a horizontal surface?
4. How do polarizing filters allow each eye to see separate images in the projection of 3D slides or movies?
5. Unpolarized light with intensity Io falls on a Polaroid sheet, the transmitted intensity is what fraction of the
original intensity?
6. What percentage of light would be transmitted by 2 ideal polarizing filters, one atop the other, with their
axes aligned? With their axes crossed at right angles?
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7. Why do Polaroid sunglasses reduce glare, whereas unpolarized sunglasses simply cut down on the total
amount of light reaching our eyes?
8. How much ordinary light will an ideal Polaroid transmit?
9. When dishes are not properly rinsed after washing, different colors are reflected from their surfaces.
Explain.
10. Why are interference colors more apparent for thin films than for thick films?
11. Why will an ideal Polaroid filter transmit 50% of incident light?
The questions below are optical illusions. Try to identify what type of illusion each of these represents.
There are lots of great websites for more optical illusions. If you are interested, here is a very brief
sampling: http://www.michaelbach.de/ot/, http://www.sandlotscience.com/,
http://www.liquidgeneration.com/sabotage/optical_sabotage.asp, etc…
12. Stare at the black lightbulb for at least 30 seconds. Then immediately stare at a white
area on the screen. You should see a glowing light bulb!
13. Watch the spiral above, staring at the center for about a minute. Then look at the back of your hand...
14. Are these letters tilted?
Which soldier is taller?
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15. Are the bold lines straight or do they bend?
Is the left center circle bigger?
16. What does the sign say? Are you sure?
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