flashcards

Question 1

Smoke alarms contain an alpha radiation source and a radiation detector.
The smoke alarm stays off while alpha radiation reaches the detector.
Why does the alarm switch on when smoke particles enter?

Answer 1

The alarm switches on because smoke particles reduce the ionization of air, decreasing the current detected by the smoke alarm.

Question 2

Why is it safe to use a source of alpha radiation in a house?

Answer 2

It is safe because alpha radiation cannot penetrate through the smoke alarm casing or human skin.

Question 3

Smoke alarms contain an alpha radiation source and a radiation detector. The smoke alarm would not work with a radiation source that emits beta or gamma
radiation.
Explain why

Answer 3

Beta and gamma radiation can penetrate the air more easily than alpha radiation, so they would not ionize the air in the smoke alarm effectively. This means they would not produce enough ions to create the current needed for the detector to work properly.

Question 4

Figure 2 shows how the count rate detected from the radiation source in the smoke alarm changes with time
The smoke alarm switches on when the count rate falls to 80 counts per second.
Explain why the radiation source inside the smoke alarm should have a long half-life

Answer 4

The radiation source should have a long half-life so that it continues to emit a stable amount of radiation over a long period of time, ensuring the smoke alarm works reliably for many years without needing replacement.