Question

3 Points

The half-value layer for lead for g rays from 60Co is 12.8 mm. An electrometer gave a count rate of 35 pulses per second when at a
certain distance from a source, with no lead between source and detector. If 6 mm of lead were then inserted between source and
detector, the count rate (in pulses per second) would be nearest to:
A. 16
OB. 8
OC. 20
D. 25
OE. 75

Answer 1

D. 25

Step-by-step explanation:

The number of pulses per second (p) for x mm of lead can be modeled by the exponential equation ...

p = 35(0.5^(x/12.8))

Then for x=6, the value of p is ...

p = 35·0.5^(6/12.8) ≈ 25.29

The expected count rate would be nearest 25 pps.