A 27 mW laser beam has a cross-sectional area of . The magnitude of the maximum electric field in this electromagnetic wave is given by:
[Given permittivity of space units, speed of light ]
[Given permittivity of space units, speed of light ]
- (A)
- (B)
- (C)
- (D)✓ Correct
Answer: (D)
Solution
The intensity of the beam is its power over its area, W/m. For an electromagnetic wave , so . This gives , so V/m, that is about kV/m.
JEE Main · 2019 · 11 Jan 2019 · Shift 2 · Single correct option