Nuclear decay and half-life

WPH15Topic 5.33 questions

Background radiation, alpha, beta and gamma radiation, nuclear equations, and the exponential law of radioactive decay.

Specification points

Understand that there is background radiation and how to take appropriate account of it in calculations
Understand the relationships between the nature, penetration, ionising ability and range in different materials of nuclear radiations (alpha, beta and gamma)
Be able to write and interpret nuclear equations given the relevant particle symbols
CORE PRACTICAL 15: Investigate the absorption of gamma radiation by lead
Understand the spontaneous and random nature of nuclear decay
Be able to determine the half-lives of radioactive isotopes graphically and be able to use the equations for radioactive decay: activity , , , and , and derive and use the corresponding log equations

A = λ N

\frac{dN}{dt} = -\lambda N

\lambda = \frac{\ln 2}{t_{1/2}}

N = N_0 e^{-\lambda t}

A = A_0 e^{-\lambda t}

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Original practice questions written in the style of the exam.

1.0

×

10−6s−1

N = A/\lambda = 4.0 \times 10^{6}/1.0 \times 10^{-6} = 4.0 \times 10^{12}

(1)

A = A_0e^{-\lambda t}

or

A = A_0(\tfrac{1}{2})^{20/8.0} = 4.0 \times 10^{6} \times 2^{-2.5}

(1)

A = 7.1 \times 10^{5}\,\text{Bq}

(1)

1

06

×

2−2.5