A 60.0 W light bulb radiates light uniformly in all different directions. What is the value of E at a distance of 0.400 m from the bulb?
A) 162 N/C
B) 212 N/C
C) 82.1 N/C
D) 106 N/C
E) 52.9 N/C

Question

Quizplus · Accepted Answer

The intensity of light is given by I = P/4πr^2, where P is the power of the light bulb and r is the distance from the bulb. The electric field strength is given by E = √(2I/ε0), where ε0 is the permittivity of free space. Plugging in the given values, we get E = √(2(60.0 W)/(4π(0.400 m)^2(8.85 × 10^-12 C^2/Nm^2))) = 106 N/C.

A 600 W Light Bulb Radiates Light Uniformly in All Different