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 a point source is inversely proportional to the square of the distance from the source (I ∝ 1/d^2). So, if the distance is doubled to 2d, the intensity will decrease by a factor of (2)^2 or 4. Therefore, the intensity at a distance 2d from the source will be I/4. The correct answer is D.

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