What is Radioactivity and what are alpha, Beta and Gamma Particles   

Radioactivity, also known as nuclear decay or radioactivity (Wikipedia, 2015, October 23), is the process by which particles are emitted by the nucleus of an unstable atom. These particles manifest as a form of radiation (Veritasium, 2011, April 9) and the most common form (Nave, 2014) of radiation is Alpha, Beta, and Gamma radiation.

Radioactivity is due to the decay of the nucleus of an unstable atom that has an insufficient number of protons and neutrons to remain stable. Radioactive occurs at a certain rate known as a Half-life (Nave, 2014), which is the time taken for half of a given sample of a radioactive material to decay from one form to another.

Examining the half-life of decay product i.e. Alpha, Beta and Gamma radiation makes it possible to determine the age of objects, known as radioactive dating. Due to the equal distribution of radiation from radioactive sources, Radioactive particles obey the inverse square law. 

Alpha, Beta and Gamma Particles – Nature and Penetration

The Alpha particle, denoted by the symbol [α], is composed of two protons and two neutrons and is high energy nuclei of helium atoms that are ejected from unstable atoms. As such they are representing by the notation it has a large mass, 7000 time greater than the Beta particle and has a very short range. Its penetrating power is less than 1/10 of a millimeter inside of the body and is only dangerous to fast-growing membranes and living cells at close range.

Beta particles denoted by the symbol [β], are high energy electron ejected when a neutron decays (Whatisnuclear.com, 2015) to a proton. The excess energy release is a negatively charged particle, since neutrons are neutrally charged and protons are positively charged. These particles have a higher penetrating power than Alpha particle and are stopped using a small aluminum plate. Good to note that if a proton decays to a neutron, a positron (an anti-electron) is the result.

Gamma rays, denoted by the symbol [γ], are photons that are emitted from the nucleus in an excited state. The release of Gamma rays occurs when highly energetic electronic in higher orbital fall from a more excited state to a less excited state, releasing Gamma Radiation.

Gamma radiation is the same electromagnetic radiation as visible light waves and x-rays, just at a much higher frequency. Consequently, their penetrating power is much higher, only being stopped (Nave, 2014) by a lead plate.

Alpha, Beta and Gamma Particles – Declaration in Electric and Magnetic fields

Alpha, Beta and Gamma Particles are deflected differently in Electric Fields (Chac In Lam, 2000) depending on the application of the Fleming Left Hand Rule. As Alpha particles are positively charged, they are deflected strongly to the left, based on the diagram below.

What is Radioactivity and what are alpha, Beta and Gamma Particles

Beta Particles, which are negatively charged, are deflected weakly to the right, as they are moving in a direction opposite to conventional current flow as described by the Fleming’s Left Hand Rule.

Gamma Radiation is made up of massless photons and as such are not deflected by strong magnetic fields, travelling in a straight line form their source.


  1. Chac In Lam. (2000, November 10). Fleming’s Left Hand Rule and the Motor Effect. Retrieved from https://www.le.ac.uk/se/centres/sci/selfstudy/mam12.htm
  2. Nave, R. (2014). Radioactive Half-Life. Retrieved from http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/halfli.html
  3. Nave, R. (2014). Radioactivity. Retrieved from http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact.html
  4. (2011, April 9). Radiation vs Radioactive Atoms. [Video]. Retrieved from https://www.youtube.com/watch?v=sehKAccM8p0
  5. com. (2015). What is radiation? What is radioactivity?. Retrieved from http://www.whatisnuclear.com/articles/radioactivity.html
  6. (2015, October 23). Radioactive decay. Retrieved from https://en.wikipedia.org/wiki/Radioactive_decay




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