About Radioactivity

Radioactivity was discovered accidentally in 1896 by a French scientist Henri Becquerel. He noticed radiation emitted by uranium compunds and that it was also able to ionise gas. Later, other scientist showed that there are 3 types of radiation: alpha, α - particles, beta, β - particles and gamma, γ rays. We cannot see radiation with our naked eyes but we can detect different types of radiation by diffusion cloud chamber.

Detection of Radiation by Diffusion Cloud Chamber

alpha, α - particles: Tracks are straight and thick. The tracks are of different lengths and high amount of kinetic energy.

beta, β - particles: Tracks are twisted and thiner

gamma, γ rays: Tracks are short, thin and irregular

Characteristics of Radiation

alpha, α - particles: Identified as stream of helium nuclei. It also more ionising than β - particles and gamma, γ rays as it has more ions. However α - particles are the least penetrating. 

beta, β - particles: Identified as stream of high-energy electrons that are slightly ionising. It is more penetrating than α - particles.

gamma, γ rays: Identified as high-frequency electromagnetic radiation. It hardly more ionise. However γ rays are the most penetrating. 

Radioactive Decay

Radioactive emission of  alpha, α - particles, beta, β - particles and gamma, γ rays are the results of radiactive decay.  Radioactive decay occurs randomly over space and time. One measure of the rate of decay is half-life. Half-life is defined as the time taken for half of the unstable nuclei to decay.

	Typical Decay Curve and half-life

Find out more about Uses and Hazards of Radioactive Material

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