21did not know saying yes or no is so painful
acc to hcv , answer in both cases is same
but i dont think this will be same
Consider the two problems.
1)A perfectly reflecting solid sphere of radius r is kept in the path of a parallel beam of light of large aperture. If the beam carries an intensity I,find the force exerted by the beam on the sphere.
2)A sphere of radius r is placed in the path of a parallel beam of light of large aperture. The intensity of the light is I .If the sphere completely absorbs the radiation falling on it,find the force exerted by the light beam on sphere.
Dont u think answers will differ in q 1 and q 2 ?
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3 Answers
2121It will be same in both cases.
We know force is proportional to ∫change in momentum
∫∂p=∫mu-∫mv
∫mu is const in both cases.
Now in case of perfect reflection by symmetry(think a bit) we can make out ∫v=0
Hence
in both cases ∫∂p=∫mu