Question

Light with an energy flux of 25 x 10^4 W m^-2 falls on a perfectly reflecting surface at normal incidence.

Answer 1

REFER TO THE ATTACHMENT

Answer 2

Answer :- 2.5 x 10⁻⁶ N.

=> It is given that,

energy flux = 25 x 10⁴ wm⁻²

Surface area = 15 cm²

=> For the Average force extend on the surface = Δp /Δt

=> Here, Light falls on a perfectly reflecting surface at normal incidence.

∴ Δp = 2Δt/c

F = 2*[ΔE/cΔt]

  = 2*p/c

  = 2 x (25 x 10 x 15 x 10) / ( 3 x 10⁸)

  = 2.5 x 10⁻⁶  N

Therefore, the average force exerted on the surface is  2.5 x 10⁻⁶ N.