Physics Review Question

Unit: Polarization
Year: 1995 Question#: 94
Question: Photographers sometimes use colored filters to restrict the light entering a lens to a single wavelength. The filters are used to eliminate

(1 ) Diffusion
(2 ) Diffraction
(3 ) Polarization effects
(4 ) Chromatic Aberration

What is this question really asking?

Explanation by: Adra M

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Answer 1 : Diffusion
Answer 1 is incorrect. Diffusion is a process that takes place in a cell. This answer may refer to diffuse reflection, which would also be incorrect. Diffuse reflection is the type of reflection which occurs on rough surfaces, which prevents a reflected image from forming. This would not be eliminated by a filter.

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Answer 2: Diffraction Answer 2 is incorrect. Diffraction happens when parallel waves reach a barrier with one or more small opening(s), and the light spreads out and creates an interference pattern. Filters will not eliminate diffraction. return to top

Answer 3 : Polarization effects
Answer 3 is incorrect. Light that passes through a filter will become polarized, therfore it would create polarization effects, not eliminate polarization effects.
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Answer 4 :Chromatic Aberration

Answer 4 is correct. Chromatic Aberration is when polychromatic light is separated into its component colors when it enters glass obliquely. Each frequency of light has a different absolute index of refraction in glass, so the component colors woud have different focal points. This results in an image of an object illuminated by white light having a fringe of colors around its edges. This can be corrected by using a filter; a single color will not disperse.

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What's this question really asking?

Do you know what color filters are used for? Colors filters absorb all the other colors of a light beam. This makes the light monochromatic. Do you know what chromatic aberration is and that it can be eliminated with the use of a filter. return to top

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