How many times will the exposure be reduced by using 4 half-value layers?

The concept of half-value layers (HVL) is crucial in understanding how radiation exposure is reduced. Each half-value layer effectively reduces the radiation intensity by half. Therefore, when you apply multiple layers, the exposure decreases exponentially based on the number of layers used.

When you use one half-value layer, the exposure is halved (reduced to 1/2). If you use a second half-value layer, the exposure is halved again (1/4 of the original exposure). This process continues cumulatively with each additional layer.

Thus, after applying four half-value layers, the radiation exposure can be calculated as follows:

1st layer: 1/2 of the original exposure

2nd layer: 1/2 of 1/2 = 1/4 of the original exposure

3rd layer: 1/2 of 1/4 = 1/8 of the original exposure

4th layer: 1/2 of 1/8 = 1/16 of the original exposure

This means that after using four half-value layers, the exposure is reduced to 1/16 of the original amount. Consequently, the original exposure has been reduced 16 times. Thus, the correct answer is