AP EAMCET20224 Jul 2022Morning ShiftPhysicsDual Nature of MatterActual
A beam of light with intensity 10 - 3 N m - 2 and cross sectional area 20 cm 2 is incident on a fully reflective surface at angle 45 ° . Then the force exerted by the beam on the surface is
Options
- A2 . 3 × 10 - 15   N
- B1 . 33 × 10 - 14   N
- C6 . 67 × 10 - 15   N
- D9 . 4 × 10 - 15   N
Correct answer
D. 9 . 4 × 10 - 15   N
Step-by-step solution
Force exerted by the beam on the surface is given by F = ∆ p ∆ t = 2 I A cos θ c Given here: I = 10 - 3   N   m - 2 ,   A = 20   cm 2 and θ = 45 ° . Putting the values, we get F = 2 × 10 - 3 × 20 × 10 - 4 × cos 45 ° 3 × 10 8 = 9 . 4 × 10 - 15   N