Question

An electromagnetic wave of intensity 150 W/m2 is incident normally on a rectangular black card with sides of 25 cm and 30 cm that absorbs all the radiation. Find the force exerted on the card by the radiation.

Answer 1

Answer:

3.75 × 10⁻⁸ N

Explanation:

Given:

Intensity of the electromagnetic wave, I = 150 W/m²

Sides of the board = 25 cm (= 0.25 m) and 30 cm (= 0.30 m)

therefore,

the area of the rectangular box, A = 0.25 × 0.30 = 0.075 m²

Now,

force exerted on the card by the radiation, F = $\frac{IA}{C}$

here,

C is the speed of the light = 3 × 10⁸ m/s

on substituting the respective values, we get

F = $\frac{150\times0.075}{3\times10^8}$

or

F = 3.75 × 10⁻⁸ N