Light with intensity of 21 W/cm2 falls on a perfectly reflecting surface at normal incidence. If surface has an area of 20 cm2, the force, due to the radiation, on the surface, is
1
0.6 × 10−6 N
2
1.4 × 10−6 N
3
2.8 × 10−6 N
4
More than one of the above
5
None of the above