Light with an energy flux of $25 \times 10^4\; wm^{-2}$ 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:

Question

( A ) $3.0 \times 10^{-6}$ N
( B ) $1.20 \times 10^{-6}$ N
( C ) $2.50 \times 10^{-6}$ N
( D ) $1.25 \times 10^{-6}$ N