Modern Physics 7 Question 9

9. 50Q/m2 energy density of sunlight is normally incident on the surface of a solar panel. Some part of incident energy (25 is reflected from the surface and the rest is absorbed. The force exerted on 1m2 surface area will be close to (c =3×108m/s)

(Main 2019, 9 April II)

(a) 20×108N

(b) 35×108N

(c) 15×108N

(d) 10×108N

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Solution:

  1. Radiation pressure or momentum imparted per second per unit area when light falls is

where, I is the intensity of the light.

In given case, there is 25 reflection and 75 absorption, so radiation pressure = force per unit area

=25100×2Ic+75100×Ic=12×Ic+34×Ic=54×Ic=54×503×108=20.83×108N/m220×108N/m2



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