Light with an enargy flux of `25xx10^(4) Wm^(-2)` falls on a perfectly reflecting surface at normal incidence. If the surface area is `15 cm^(2)`, the average force exerted on the surface is

Options

A. `1.25xx10^-6N`
B. `2.50xx10^-6N`
C. `1.20xx10^-6N`
D. `3.0xx10^-6N`

Answer

b

Explanation

Average force =average pressurexxarea
`:. F_(av)=(2I)/cxxA=(2xx(25xx10^4)xx(15xx10^-4))/(3xx10^8)`
`=2.5xx10^-6N`