CAIE IGCSE Physics 5.2.2.4 Their Relative Ionising Effects with Questions

Practise explaining why alpha ionises more strongly than beta or gamma by comparing electric charge, kinetic energy and interaction time with atoms.

Exam points

calculate corrected count rate by subtracting background count rate
convert detector counts and time into counts per second or minute
analyse radioactive decay count-rate data and half-life measurements

[Maximum number: 2]

Many household smoke alarms contain a sample of the radioactive isotope americium-241 (Am).

Americium-241 decays to an isotope of neptunium (Np) by alpha-particle ( $\alpha$ -particle) emission.

One reason for using an isotope that emits $\alpha$ -particles in a smoke detector is that $\alpha$ -particles are more strongly ionising than beta-particles ( $\beta$ -particles).

Explain why $\alpha$ -particles are more strongly ionising than $\beta$ -particles.

( $\alpha$ -particles have) more kinetic energy (than $\beta$ -particles)
( $\alpha$ -particles have) more charge (than $\beta$ -particles)

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CAIE IGCSE Physics 5.2.2.4 Their Relative Ionising Effects with Questions question 1