Radioactive Phenomena – Alpha Decay

Radioactivity is a phenomenon discovered by the French scientist Henri Becquerel using phosphorescent materials. Radioactivity is also known as radioactive decay or nuclear decay.  Let us know more about radioactivity and its types. Nuclear instability gives rise to radioactivity where an unstable atomic nucleus loses energy by emitting particles from nuclei due to excess protons or neutrons.

There are three types of radioactive decay:

  1. Alpha decay
  2. Beta decay
  3. Gamma decay

Alpha decay is a type of immediate radioactive decay process in which an atomic nucleus emits an alpha particle and decays into a different atomic nucleus, with a change in mass number and atomic number ie., the mass number is reduced by four and an atomic number that is reduced by two. Positive helium nuclei are referred to as alpha particles.

The element or isotope which emits radiation and sustains the process of radioactivity is known as Radioactive Element.

Alpha Decay Formula

Generalizing the alpha decay process and its outcome, the process can be put into the equation by


X = parent nucleus

Y= daughter nucleus

alpha = emitted alpha particle in the reaction

For example,

Alpha decay of Uranium 238 is as shown below.

Uranium 238 decays into Thorium 234 with the emission of an alpha particle is given as

Example 2:

Let us know the radioactive decay of thorium-232 is as shown below:

On radioactive decay of thorium-232, it decays into Radium-228 and He (alpha particle)

When the underground depositions of minerals containing uranium or thorium undergoes alpha decay Helium is produced on Earth. The helium is a by-product of natural gas production.

Let us study another important concept of Physics – Stress. Like radioactivity and alpha decay topics, stress and stress units are also important concepts to be known in view of competitive exams. It is important to know the units of all the measurable quantities in physics. Some times questions based on the units might turn out to be tricky and confusing. Hence be familiar with the quantities and associated units. Let us now learn about stress and stress units.

Stress is defined as the force applied per unit area of the body. Stress causes a change in the shape of the body. Depending upon the material of the object, it responds to the force applied. The object with less force bearing capacity deform more or might end up breaking in some cases. The stress-strain curve shown below, explains the exact extension of the material when stress-strain is applied.

Stress-strain varies from one material to another. Stress can be found using the following formula:


σ is the stress

F = force

A = surface area

Stress units are the measure of the force per unit area. SI unit of stress is measured in pascals.

Stress unit = N/m2

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