Unit: optics
Year: 1995 Question#: 88
Question: The Diagram below shows parallel monochromatic incident light rays being reflected from a concave mirror. Which phenomenon does the diagram illustrate?
(1 ) chromatic aberration
(2 ) spherical aberration
(3 ) refraction
(4 ) dispersion
What is this question really asking?
Explanation by: Andy D.
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Answer 1
chromatic aberration
INCORRECT
This answer is incorrect, because it is using a piece of jargon that has nothing to do with the question. It is there to fool you if you don't know your vocabulary. return to top
Answer 2
spherical aberration
CORRECT
This is the correct answer. A spherical aberration is when light reflects off of a spherical object, but has an indefinite focus. Note how there is no definite focus in this problem. The light, depending on where it comes from, focuses at different points.
return to top Answer 3
refraction
INCORRECT
Refraction is when, depending on the indices of a material, light bends when it enters a different material. This has nothing to do with mirrors. return to top
Answer 4
dispersion
INCORRECT
This answer is incorrect, because dispersion is a totally different physical action. Dispersion is when a white light is split into all of its colors, like in a prism. Dispersion would be relevant to polychromatic light and lenses, but not to monochromatic light or to mirrors.
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What's this question really asking?
This question is really asking what the effect is called when the light doesn't quite focus after being reflected off of a mirror. return to top
