A Geiger counter placed 1 meter from a point source of radiation registers 100 counts per second. If the Geiger counter is moved closer - to 0.5 meter from the source, what will the count rate be?
A) 200 counts/s
B) 100 counts/s
C) 400 counts/s
D) 25 counts/s
E) 50 counts/s

Question

Quizplus · Accepted Answer

The intensity of radiation follows the inverse square law, which states that the intensity is inversely proportional to the square of the distance from the source. When the distance is halved (from 1 meter to 0.5 meters), the intensity (or count rate) increases by a factor of $ (1/0.5)^2 = 4 $. Therefore, the count rate increases from 100 counts/s to 400 counts/s.

A Geiger Counter Placed 1 Meter from a Point Source