A beam of gamma rays strikes a lead target with a half-value layer of 0.40 cm. What fraction of the photons in the beam will penetrate to a depth of 1.20 cm or more?

Question

Quizplus · Accepted Answer

The half-value layer is the thickness of material that reduces the intensity of the radiation by half. To penetrate to a depth of 1.20 cm, or 3 half-value layers (1.20 cm / 0.40 cm per layer), the intensity would be reduced by half three times: 1/2 * 1/2 * 1/2 = 1/8 or 0.125.

A Beam of Gamma Rays Strikes a Lead Target with a Half-Value