If the distance from a point source of EM radiation is doubled, the intensity is
A) doubled
B) the same as it was before.
C) reduced by a factor of four.
D) increased by a factor of four.
E) cut in half.

Question

Quizplus · Accepted Answer

The intensity of EM radiation decreases as the distance from the point source increases. According to the inverse square law, the intensity is inversely proportional to the square of the distance. So, if the distance is doubled, the intensity will be reduced by a factor of four (2^2=4). Therefore, the correct choice is option C.

If the Distance from a Point Source of EM Radiation