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 rms electric field strength, E, at a distance r from a point source of power, P, is given by:
E = sqrt(2Pr)/(4πε₀r²)
where ε₀ is the permittivity of free space.
Substituting E = 4.33 N/C and P = 25 W, we get:
4.33 = sqrt(2*25*r)/(4πε₀r²)
Squaring and rearranging, we get:
r = (2*25)/(4πε₀*4.33²) = 6.3 m (approx)

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