Suppose two rays of light of a single color, from a single source, take two diff

Question

Suppose two rays of light of a single color, from a single source, take two different paths to reach a point on a screen. (a) How much must their path lengths differ for them to interfere destructively at that spot on the screen? Could they differ by any other amount(s) and still interfere destructively? Explain. (b) How much must their path lengths differ for them to interfere constructively at that spot on the screen? Could they differ by any other amount(s) and still interfere constructively? Explain. 10. You have a nice camera, with many uncoated glass lenses between the image sensor and the object you are photographing. When light strikes the front surface of any of the lenses, 4% of the light is reflected back, away from the camera toward the object you are photographing. When the transmitted light leaves the glass lens, entering the air in the camera and heading toward the next lens, 4% is again reflected back toward the original object. It the camera has 5 glass lenses, how much of the original light from the object actually makes it to the image sensor inside the camera?

Explanation / Answer

If W is the wavelength of that coloured wave, then the wave behaves periodically in space with a period of W distance, i.e. it has same oscillation at 0, W, 2W and so on. and half wavelength forward, oscillation amount(Amplitude) is the negative of what was half wavelength distance back.

So, if wave travels W/2 extra distance, it would show destructive interference. and since it is periodic with W, it will show destructive interference for 3W/2, 5W/2 7W/2 and so on at all these distances.

b) Similar to the above, with W extra distance, it will be constructive interference, and other distances would be W, 2W, 3W, 4W, and so on.

10. 4% is getting reflected, => 96% is getting to the next lens. so, 96% of 96% (0.96*0.96) would be going through the second lens.

=> light passing through the 5th lens = 0.965 = 0.82 or 82% of original light

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