(A) Determine the following ratio: Power of light entering the eye in sunlight/p
ID: 1562770 • Letter: #
Question
(A) Determine the following ratio:Power of light entering the eye in sunlight/power of light entering the eye in moonlight
(B) Suggest why your answer in part (a) indicates that the change in diameter of the iris is not the principal mechanism by which the eye is able to adjust to different light intensities. A student measures the aperture of the iris of one of her eyes as 2.0 mm in sunlight l. and 7.0 mm in moonlight. The intensity at her eye of sunlight is 106 times greater than the intensity of moonlight.
Explanation / Answer
for sun d1 = 2mm
for moon d2 = 7mm
I1 = 10^6*I2
Intensity = power/area
P1/P2 = I1*A1/I2*A2
= (I1/I2) (d1/d2)^2
= (10^6)(2/7)^2
P1/P2 = 81632.6 = 8*10^4
(b) if iris were to be the principal mechanism, then ratio would need to be about (7/2) or (2/7)
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