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A palne light wave of intensity I = 0.70 W//cm^(2) illuminates a sphere with ideal mirror surface. The radius of the sphere is R = 5.0cm. From the standpoint of the corpuscular theory find the force that light exerts on the sphere. |
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Answer» Solution :We consider a strip defined by the angular range `(theta, theta+d theta)`. From the previous problem the normal pressure exerted on this strip is `(2I)/(c ) cos^(2) theta` This pressure givens rise to a force whose resultant, by symmetry is in the direction of the INCIDENT light. Thus `F = (2I)/(c) underset(0)overset(PI//2)int cos^(2).cos theta.2piR^(2)sin thetad theta = piR^(2)(I)/(c )` Putting in the values `F = pi xx 25 xx 10^(-4)(0.70xx10^(4))/(3xx10^(8))N = 0.183muN` 
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