If the radiation intensity is 50 R/hr, how many half-value layers are needed to reduce it to 5 R/hr?

To determine how many half-value layers are needed to reduce the radiation intensity from 50 R/hr to 5 R/hr, it’s important to understand the concept of half-value layers (HVLs). Each half-value layer represents the thickness of a material that reduces the intensity of radiation by half.

Starting with an intensity of 50 R/hr, the process of calculating the number of half-value layers needed involves repeatedly halving the intensity:

1. After one half-value layer, the intensity would be halved:

50 R/hr → 25 R/hr.

2. After a second half-value layer, the intensity is halved again:

25 R/hr → 12.5 R/hr.

3. After a third half-value layer:

12.5 R/hr → 6.25 R/hr.

4. After a fourth half-value layer:

6.25 R/hr → 3.125 R/hr.

The target intensity is 5 R/hr. After three half-value layers, the intensity is 6.25 R/hr, which is still above 5 R/hr. However, after four half-value layers, the intensity drops to 3.125 R/hr, which is