Wave motionHard
Question
Moonlight has an intensity of 0.84 × 10-3 W/m2. The average wavelength of moonlight is 5000 
Options
A.The force exerted by moonlight on a perfectly absorbing surface of area 100 m2 is 0.28 × 10-9 N
B.The force exerted by moonlight on a perfectly absorbing surface of area 100 m2 is 0.84 × 10-2N
C.The number of photons/m3 in the beam is 7 × 106
D.The number of photons/m3 in the beam is 7 × 103
Solution
The force exerted = 
× A
=
× 100 = 0.28 × 10-9N
The no. of photons per unit volume =
= 7 × 106
× A=
× 100 = 0.28 × 10-9NThe no. of photons per unit volume =
= 7 × 106Create a free account to view solution
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