Light with an enargy flux of `25xx10^(4) Wm^(-2)` falls on a perfectly reflecting surface at normal incidence. If the surface area is `15 cm^(2)`, the average force exerted on the surface is

Light with an energy flux of 25xx10^4 Wm^-2 falls on a perfectly reflecting surface at normal incidenc .If the surface area 15cm^2 ,the average force exerted on the surface is

Light with an energy flux of 18 W//cm^(2) falls on a nonreflecting surface at normal incidence. If the surface has an area of 20 cm^(2) , find the average force exerted on the surface during a 30 minute time span.

Light with an energy flux of 18 W//cm^(2) falls on a nonreflecting surface at normal incidence. If the surface has an area of 20 cm^(2) , find the average force exerted on the surface during a 30 minute time span.