If an optimal radiograph is acquired at 72 inches (183 cm) with an air kerma of 1 milligray (mGy), what will the air kerma be if the distance is reduced to 60 inches (152 cm)?

To understand the correct answer, it's essential to consider the inverse square law, which states that the intensity of radiation exposure (air kerma in this case) is inversely proportional to the square of the distance from the source of radiation. This means that as you decrease the distance from the radiation source, the exposure will increase based on the distance squared.

In this scenario, you start with an air kerma of 1 mGy at a distance of 72 inches. If the distance is then reduced to 60 inches, you can use the inverse square law to calculate the new air kerma.

The formula to apply is:

[ \text{New Air Kerma} = \text{Old Air Kerma} \times \left(\frac{\text{Old Distance}}{\text{New Distance}}\right)^2 ]

Substituting the values, we have:

Old Air Kerma = 1 mGy

Old Distance = 72 inches

New Distance = 60 inches

When you plug in the numbers:

[ \text{New Air Kerma} = 1 \text{ mGy} \times \left(\frac{72}{60}\right)^2 ]

Calculating the factor:

[ \left(\