InterviewSolution
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InterviewSolution
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A perfectly reflecting mirror has an area of `1cm^(2)` Light enery is allowed to fall on it 1 h at the rate of `10 W cm^(2)`. The force that acts on the mirror isA. `3.35 xx 10^(-8) N`B. `6.7 xx 10^(-8) N`C. `1.34 xx 10^(-7)N`D. `2.4 xx 10^(-4) N` |
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Answer» Correct Answer - B Let, E = Energy falling on the surface per second `= 10 J` Momentum of photons, `p = (h)/(lambda) = (h)/((c//v)) = (hv)/(c) = (E)/(c)` On reflection, change in momentum per second `=` force `= 2p = (2E)/(c) = (2 xx 10)/(3 xx 10^(8)) = 6.7 xx 10^(-8) N` |
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