A Laser with a Power of 1

Multiple Choice

A laser with a power of 1.0 mW has a beam radius of 1.0 mm.What is the peak value of the electric field in that beam? (c = 3.0 × 10⁸ m/s,μ₀ = 4π × 10^-7 T ∙ m/A, ε₀ = 8.85 × 10^-12 C²/N ∙ m²)

A) 490 V/m
B) 840 V/m
C) 65 V/m
D) 120 V/m
E) 22 V/m