Example 8 4 Light with an energy flux of 18 W cm falls on a

Last updated: 6/10/2023

Example 8 4 Light with an energy flux of 18 W cm falls on a non reflecting surface at normal incidence If the surface has an area of 20 cm2 find the average force exerted on the surface during a 30 minute time span Solution The total energy falling on the surface is U 18 W cm x 20 cm 30 60 6 48 105 J Therefore the total momentum delivered for complete absorption is U 6 48 105 J 2 16 x 10 kg m s 3x10 m s p c The average force exerted on the surface is p 2 16x10 3 t 0 18x104 F 1 2 10 N