A radiation of energy 'E' falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (c=velocity of light)

(a)E/c

(b)2E/c

(c)2E/c²

(d)E/c²

Light with an energy flux of 25 x 10⁴ Wm^-2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15cm² the average force exerted on the surface is

(a)1.25x10^-6N

(b)2.50x10^-6N

(c)1.20x10^-6N

(d)3.0x10^-6N