What happens to the exposure rate if the distance from a radiation source is doubled?

When the distance from a radiation source is doubled, the exposure rate decreases by a factor of four due to the inverse square law of radiation. This law states that the intensity of radiation (or exposure rate) from a point source is inversely proportional to the square of the distance from the source.

In mathematical terms, if the distance (d) is doubled, the intensity (I) can be expressed as:

I ∝ 1/d².

If the initial distance is d, and it is increased to 2d, the new intensity would be:

I_new ∝ 1/(2d)² = 1/(4d²).

Thus, the new exposure rate is one-fourth of the original exposure rate, demonstrating a decrease by a factor of four. This principle is fundamental in radiation safety and medical dosimetry, as it emphasizes the importance of distance in managing exposure risks.