NEET2014PhysicsElectromagnetic WavesActual
Light with an energy flux of 25 × 10 4   W   m - 2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15   c m 2 , the average force exerted on the surface is:
Options
- A1.25 × 10 - 6 N
- B2.50 × 10 - 6 N
- C1.20 × 10 - 6 N
- D3.0 × 10 - 6 N
Correct answer
B. 2.50 × 10 - 6 N
Step-by-step solution
Here, we have to calculate the average force calculated at the surface. Given I = 25 × 10 4 A = 15 × 10 - 4 We know that, F = 2 I A C = 2 25 × 10 4 15 × 10 - 4 3 × 10 8 = 2.5 × 10 - 6 N Hence, force will be 2.5 × 10 - 6 N So Option (2) will be correct.