Question

A Geiger counter placed 1 meter from a point source of radiation registers 100 counts per second. What will the count rate be if the Geiger counter is moved closer—to 0.5 meter from the source?

Answer 1

According to the inverse-square law, the count rate on a Geiger counter will increase to 400 counts per second if the distance from a point source of radiation is reduced from 1 meter to 0.5 meter.

Step-by-step explanation:

When dealing with a Geiger counter and a point source of radiation, the intensity of the radiation detected by the Geiger counter is inversely proportional to the square of the distance from the source, according to the inverse-square law. At a distance of 1 meter, the Geiger counter registers 100 counts per second. When the distance is halved to 0.5 meter, the count rate increases by a factor of ² (since (1/0.5)² = 4). Therefore, the new count rate will be 100 counts per second × 4, which equals 400 counts per second.