Question

Find net force exerted by light on a perfect reflecting surface, if its incident at an angle of ${60}^o$ with normal (intensity light $\to I,$ are is $A$)

• A. $\frac{IA}{c}$
• B. $\frac{2FA}{c}$
• C. $\frac{4IA}{c}$
• D. $\frac{3IA}{c}$

Answer 1

The correct option is A $\frac{IA}{c}$

Net force of a reflecting surface is given by the formula

$P=\frac{2IA}{c}{\cos }^2\theta$

Substituting the values,

$P=\frac{2IA}{c}{\cos }^2\left({60}^{\circ }\right)$

$P=\frac{2IA}{c}\times \frac{1}{2}$

$P=\frac{IA}{c}$

The force exerted by the light on the surface is $\frac{IA}{c}$