The intensity of the waves from a point source at a distance d from the source is I. What is the intensity at a distance 2d from the source?
A) 4I
B) 2I
C) I/2
D) I/4
E) I/ $\sqrt { 2 }$

Question

Quizplus · Accepted Answer

The intensity of waves from a point source decreases with the square of the distance from the source. So, if the distance from the source is doubled, the intensity would decrease by a factor of (2)^2 = 4. Therefore, the intensity at a distance 2d from the source would be I/4.

The Intensity of the Waves from a Point Source at a Distance