Physics problem... Eye pupil...?
An individual's eye pupil changes from a diameter of 3.1 mm to a diameter of 2.5 mm as the illumination is increased. The new minimum angle of resolution is x times the original angle of resolution. What is this factor x?
Comments
There is a problem with this question: it might indicate that your teacher is ill-informed about the properties of the human eye.
According to the 1st reference below the resolution of the human eye improves (smaller angle) when the iris contracts. This is because the resolution is limited by spherical aberration of the refracting system, which is less when the aperture is smaller.
However, it is possible that this question is intended to be about the Raleigh limit to resolution, which makes the minimum angle of resolution of an ideal optical system inversely proportional to the diameter of the aperture (an approximation for small angles - see 2nd reference). This makes the resolution deteriorate (larger angle) when the aperture is reduced. If your teacher is inappropriately treating the eye as an ideal optical system then the expected answer is probably x = 3.1/2.5 = 1.24 (approx). So it looks like you are expected to give an answer which is the opposite of what happens in reality; talk to your teacher about this, and ask him or her to read the 1st reference.
Source(s):
http://en.wikipedia.org/wiki/Eye#Visual_%E2%80%A6
http://en.wikipedia.org/wiki/Angular_res%E2%80%A6
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