A 1100 W light bulb is placed at the centre of a spherical chamber of radius 20 cm. Assume that 60% the energy supplied to the bulb is converted into light and that the surface of the chamber is perfectly absorbing. The force and pressure exerted by the light on the surface of chamber is:

$3.6×10^{-6}N,4.4×10^{-6}N/m^2$

Consider a spherical chamber of radius 20 cm.

Bulb is placed at point s as shown in figure.

Intensity of light at surface, $I=\frac{0.6P}{4πr^2}$

Force, exerted on the surface, $F=\frac{p}{c}$

Where P is power of bulb.

$∴F=\frac{1100}{3×10^8}=3.6×10^{-6}N$

Pressure exerted by light, $P=\frac{I}{c}=\frac{0.6P}{4πr^2c}=\frac{0.6×1100}{4π(0.2)^2×3×10^8}=4.4×10^{-6}N/m^2$