Edexcel A-Level Physics Gamma Absorption by Lead Practical

Practise Edexcel A-Level Physics gamma absorption by lead by interpreting count-rate graphs, shielding thickness and attenuation equations.

Exam points

use half-thickness reasoning to predict corrected count rate after added lead absorber
judge whether lead shielding is sufficient from percentage-transmission graph data
determine attenuation coefficient µ or source identity from R = R0e^-µx graphs

[Maximum number: 3]

A student investigated the absorption of gamma radiation by lead, as shown. She used an americium source.

She placed sheets of lead absorber between the source and the GM tube. She recorded the count for 2 minutes for each thickness of absorber.

Figure for Question 5.4.140 - Core Practical 15 - gamma absorption by lead question 1 — Edexcel A-Level Physics A2

The student plotted a graph of count rate R against thickness x of absorber. Her graph is shown below.

R varies with x according to the equation

R=60 \mathrm{e}^{-\mu x}

where $\mu$ is a constant.
Determine a value for $\mu$ .

\mu=

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5.4.140 - Core Practical 15 - gamma absorption by lead question 1