Sun light falls normally on a surface of area 36 cm 2 and exerts an average force of 7 . 2 × 10 - 9 N within a time period of 20 minutes. Considering a case of complete absorption, the energy flux of incident light is

Step-by-step solution

The radiation pressure in case of complete absorption is given by, P = I c . Therefore, the force will be, F = I c × A ⇒ I = F c A ⇒ I = 7 . 2 × 10 - 9 × 3 × 10 8 36 × 10 - 4 = 600   W   m - 2 ⇒ I = 0 . 06   W   cm - 2