Which radiation is used in a household smoke alarm, and why is it suitable?

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Question

Which radiation is used in a household smoke alarm, and why is it suitable?

Accepted Answer

Alpha, because its very short range means smoke particles absorb it and the casing contains it — Award 1 mark. The alarm sounds when smoke blocks the alpha particles and the tiny current between the plates falls. Gamma would pass straight through the smoke and give no signal, as well as escaping into the room.

Answer

Neutron radiation, because it is not ionising at all

Answer

Gamma, because it passes easily through the plastic casing of the alarm

Answer

Alpha, because its very short range means smoke particles absorb it and the casing contains it

Answer

Beta, because it is stopped by a few millimetres of aluminium

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