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Alpha Decay

Radioactive decay in which radioisotopes shed large helium-like particles.

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GASP! Radioactivity in your household!

Alpha Decay- Smoke Detectors

Recall that alpha particles or Helium nuclei (42He) are emitted during radioactive decay.

Credit: Saperaud
Source: http://commons.wikimedia.org/wiki/File:Ceiling-smoke-alarm.JPG
License: CC BY-NC 3.0


You probably have read about alpha particles being used in the Rutherford gold foil experiment, but it may surprise you to learn that alpha particles may be found in every room you walk in!  One conventional use for alpha particles can be found in household smoke detectors. Rest assured, this minute amount of radiation is harmless! In ionization detectors, a tiny amount of Americium-241 continuously releases a stream of alpha particles. These alpha particles ionize air atoms by striking off electrons from free floating atoms in the air. Inside the detector are 2 plates, one negatively charged and one positively charged; the ions will be drawn toward the negative plate and the electrons will be attracted towards the positive plate, thus creating an electrical current. If the current is broken such as when smoke particles attach to the ions, the detector will sound off. 

Creative Applications

1. What other types of smoke detectors exist?

2. What types of atoms (specifically) are ionized by the alpha particles in the detector?

3. What are other conventional uses of Alpha particles that you may see everyday?

4. What are some commonly associated concerns with alpha particles and radioactive materials in general?

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Image Attributions

  1. [1]^ Credit: Saperaud; Source: http://commons.wikimedia.org/wiki/File:Ceiling-smoke-alarm.JPG; License: CC BY-NC 3.0

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