Radiation pressure force on Earth · CAP 2015 #4

Physics · electromagnetism

Problem

If electromagnetic radiation with intensity I (power per unit area) is absorbed by a surface, it exerts a pressure on the surface that is given by

\frac{I \cos\theta}{c}

, where c is the speed of light and θ is the angle the light rays hit the surface relative to a direction perpendicular to the surface. The Sun has a radiation power of

P = 3.9 \times 10^{26}

W. The absorption of sunlight by Earth causes a force on Earth that pushes it away from the Sun. Which of the following is closest to the magnitude of this force? a)

10^7

N b)

10^9

N c)

10^{11}

N d)

10^{13}

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