JEE Class main Answered

Pressure P exerted on a perfectly reflecting surface of sphere is

P = ( 2 I ) / c

where I is intensity of elctromagnetic radiation and c is speed of light .

If the sphere is exposed to electromagnetic radiation only half the surface area receive the radiation.

force F = Pressure × area

force F = [ ( 2 I ) / c ] × ( 2 π R² ) =  ( 4 π R² ) ( I / c )