At a distance of 10 m from a light bulb, the rms value of the electric field is 16 V/m. What is the rms value of the electric field at a distance of 20 m from the light bulb?
A) 32 V/m
B) 16 V/m
C) 8.0 V/m
D) 4.0 V/m
E) 2.0 V/m

Question

Quizplus · Accepted Answer

The electric field due to a point source of light follows the inverse square law, which means the rms value of the electric field is inversely proportional to the distance from the light bulb. Therefore, if the distance is doubled, the rms value of the electric field will be halved. Thus, the rms value of the electric field at 20 m from the light bulb will be 16 V/m / 2 = 8.0 V/m. Therefore, the best choice is C) 8.0 V/m.

At a Distance of 10 M from a Light Bulb