Question
Some smoke detectors make use of radiation which is very easily stopped by tiny smoke particles moving between the radioactive source and the detector. square square The most suitable type of radioisotope for a smoke detector would be A an alpha-emitter with a long half-life B a gamma-emitter with a short half-life C an alpha-emitter with a short half-life D a gamma-emitter with a long half-life.
Answer
4.4
(200 Votes)
Olwen
Elite · Tutor for 8 years
Answer
A
Explanation
Smoke detectors detect smoke, interrupting radiation; therefore, they work with radioisotopes that emit a type of radiation that essentially travels in straight lines and is easily stopped by small particles in the air—such as the particles that make up smoke. Thus, an alpha emitter works since alpha particles (two neutrons and two protons—the same as a helium atom nucleus) do not penetrate material as deeply as other types of radiation, and small amounts of smoke can stop an alpha particle enough for the detector to sense there is a fire. Regardless of the radioisotope employed, it must have a long half-life. If the half-life of the substance was short, it could stop sending out radiation in the space of only a few months, leaving the detector ineffective.