1. A point source of light is located 3.6 m below the surface of a large pool of
ID: 2242162 • Letter: 1
Question
1. A point source of light is located 3.6 m below the surface of a large pool of water. Find the area of the largest circle on the pool's surface through which light coming directly from the source can emerge.
m2
2. Two polarizing sheets have their transmission axes crossed so that no light gets through. A third sheet is inserted between the first two such that its transmission axis makes an angle ? with that of the first sheet. Unpolarized light of intensity I0 is incident on the first sheet. Find the intensity of the light transmitted through all three sheets for the following values of ?.
Explanation / Answer
You need to work out the critical angle for light going from water to air.
Then you should define a triangle with this angle at the point source and 5m distance to the surface. Work out the length of the "opposite" side of the triangle using trigonometry. This is the radius of the circle. Use this to find the area.
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