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Detecting beta radiation with a spark detector
A radioactive source emits alpha, beta and gamma radiation.
A spark detector is a device that can be used to detect alpha radiation.
A spark detector works by alpha particles ionising atoms in the air near a wire mesh.
A large potential difference creates a spark when the air near the wire mesh is ionised.
Suggest why a spark detector cannot detect beta radiation.
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Marking points
- 1 State that beta radiation is only weakly ionising.
Full-mark answer
Beta radiation is only weakly ionising, so it does not ionise the air enough to produce a spark.
Why this answer loses marks
Beta radiation is blocked by the air.
The mark scheme credits the weak ionising power of beta radiation, not absorption by air.