Question

A point isotropic light source of power P = 12 watts is located on the axis of a circular mirror of radius R = 3 cm. If the distance of the source from the centre of the mirror is a = 39 cm and the reflection coefficient of the mirror is α = 0.70 then the force exerted by the light ray on the mirror is ______ × 10^-10 N.

Options

• 1.00

• 2.00

• 3.00

• 4.00

Answer 1

A point isotropic light source of power P = 12 watts is located on the axis of a circular mirror of radius R = 3 cm. If the distance of the source from the centre of the mirror is a = 39 cm and the reflection coefficient of the mirror is α = 0.70 then the force exerted by the light ray on the mirror is 1.00 × 10^-10 N.

Explanation:

`[(P/(4pia^2) xx piR^2)/(hv)][70/100 xx (2hv)/c + 30/100 xx (hv)/c]`

= `1 xx 10^-10` N