The rms electric field strength at a distance r from a 25 W light source is found to be 4.33 N/C. What is the distance r?
A) 22 m
B) 6.3 m
C) 30 m
D) 40 m

Question

Quizplus · Accepted Answer

The electric field strength (E) of a spherical wave decreases as the distance from the source (r) increases according to the inverse square law:
E = k / r^2
where k is a constant that depends on the strength of the source.

We can rearrange this equation to solve for r:
r = sqrt(k / E)

We are given E = 4.33 N/C and k = 25 W, so
r = sqrt(25 / 4.33) = 6.3 m

Therefore, the answer is choice B.

The Rms Electric Field Strength at a Distance R from a 25