Write the application of alpha decay in smoke detectors.

Explanation

(i) The smoke detector uses around 0.2 mg of man-made weak radioactive isotope called americium `(""_(95)^(241)Am)`.

(ii) This radioactive source is placed between two oppositely charged metal plates and `alpha` radiations from `""_(95)^(241)Am` continuously ionize the nitrogen, oxygen molecules in the air space between the plates.
(iii) As a result, there will be a continuous flow of small steady current in the circuit.
(iv) If smoke enters, the radiation is being absorbed by the smoke particles rather than air molecules.
(v) As a result, the ionization and along with it the current is reduced. This drop in current is detected by the circuit and alarm starts.
(vi) The radiation dosage emitted by americium is very much less than safe level, so it can be considered harmless.