Chapter 25, Problem 32MCQ

The beam from a laser is focused with a lens, reducing the area of the beam by a factor of 2. By what factor does the amplitude of the electric field increase?

A. The amplitude does not change.

B. The amplitude increases by a factor of $\sqrt{2}$.

C. The amplitude increases by a factor of 2.

D. The amplitude increases by a factor of 2 $\sqrt{2}$.

E. The amplitude increases by a factor of 4.