Concepts Of Physics MCQ Edition [Volume 2]PhysicsElectromagnetic Waves
A plane electromagnetic wave strikes a material surface, imparting momentum p and energy E . Which of the following holds true?
Options
- Ap 0 , E = 0
- Bp = 0 , E = 0
- Cp = 0 , E 0
- Dp 0 , E 0
Correct answer
D. p 0 , E 0
Step-by-step solution
Electromagnetic waves carry both energy and momentum. When a plane electromagnetic wave strikes a material surface, it transfers energy to the surface, so the energy imparted is E 0 . The momentum transferred to the surface is given by p = E c for a completely absorbing surface and p = 2E c for a completely reflecting surface. Since E 0 and the speed of light c is finite, the momentum imparted is also non-zero, so p 0 . Thus, both p 0 and E 0 .