Texas Industrial Radiography Gamma Practice Test

According to the inverse square law, if you double the distance from a radiation source, the intensity will be:

1. Reduced by ½

2. Twice the original intensity

3. Unchanged

4. ¼ the original intensity

The correct answer is: ¼ the original intensity

The inverse square law states that the intensity of radiation from a point source is inversely proportional to the square of the distance from that source. Specifically, if the distance between the source and the observer is doubled, the intensity of radiation received is reduced by a factor of four. To understand this principle, consider the relationship described by the formula: \[ \text{Intensity} \propto \frac{1}{\text{Distance}^2} \] If we denote the initial distance as \(d\) and the initial intensity as \(I\), then when the distance is doubled (to \(2d\)), the new intensity can be expressed as: \[ \text{New Intensity} = \frac{I}{(2)^2} = \frac{I}{4} \] This indicates that the intensity is reduced to one-fourth of its original value. Therefore, the correct answer demonstrates an understanding of how increasing the distance from the source effectively decreases the intensity of radiation due to the behavior of radiation dispersal in three-dimensional space.