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^(-6)N`
B. `2.50xx10^(-6)N`
C. `1.20xx10^(-6)N`
D. `3.0xx10^(-6)N`

Answer

B

Explanation

`"Average force "F_("av")=(Deltap)/(Deltat)=(2IA)/(c )(because" Power = F.V")`
`=(2xx25xx10^(4)xx15xx10^(-4))/(3xx10^(8))=2.50xx10^(-6)N`