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Bob777
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Homework Statement
A light is to be placed atop a pole of height h feet to illuminate a busy traffic circle, which has a radius of 40ft. The intensity of illumination I at any point P on the circle is directly proportional to the cosine of the angle θ (see the figure) and inversely proportional to the square of the distance d from the source.
(a)How tall should the light pole be to maximize I?
Homework Equations
The Attempt at a Solution
intensity of illumination I=cosθ/d^2
cosθ/d^2*the area=I
but any point P has different intensity of illumination according to the distance form center.
and when h change all the intensity of illumination of any point change.
How can I know the I?
Please help me! thanks