1. Tardigrade
  2. Question
  3. Physics
  4. Light with an energy flux of 25 × 104 W m -2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm 2, the average force (in micro newton) exerted on the surface is

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Q. Light with an energy flux of $25 \times 10^{4} \,W \,m ^{-2}$ falls on a perfectly reflecting surface at normal incidence. If the surface area is $15 \,cm ^{2}$, the average force (in micro newton) exerted on the surface is

Dual Nature of Radiation and Matter

Solution:

Average force, $F_{ av }=\frac{\Delta p}{\Delta t}=\frac{2 I A}{c}$
$=\frac{2 \times 25 \times 10^{4} \times 15 \times 10^{-4}}{3 \times 10^{8}}$
$=2.50 \times 10^{-6}\, N$