Radiations of intensity 0.5W/m2 are striking a metal plate. The pressure on the plate is
0.166× 10−8 N/m2
0.332× 10−8 N/m2
0.111× 10−8 N/m2
0.083× 10−8 N/m2
Intensity or power per unit area of the radiations P= fv ⇒ f=Pv=0.53× 108=0.166× 10−8N/m2