Types Of Radiation


Energy emitted from a body or source that is transmitted through an intervening medium or space and absorbed by another body. Transmission is in the form of waves but wave/particle duality under quantum physics.

Radiation is classified as being either non-ionizing or ionizing. Non-ionizing radiation is longer wavelength/lower frequency lower energy. While ionizing radiation is short wavelength/high frequency higher energy.

Ionizing Radiation

Ionizing Radiation has sufficient energy to produce ions in matter at the molecular level. If that matter is a human significant damage can result including damage to DNA and denaturation of proteins. This is not to say that non-ionizing radiation can’t cause injury to humans but the injury is generally limited to thermal damage i.e. burns.

There is a great deal of information on the above chart. One of the most interesting things is that the visible spectrum is essentially the divide between ionizing and non-ionizing radiation. This makes sense clinically when we think of UV radiation causing skin cancer.

Non – Ionizing Radiation

Since every state workplace has one or more natural or man-made sources of non-ionizing radiation, these requirements apply to every state employee. Electromagnetic radiation is produced by moving electric charges and may be of natural origin (e.g. the sun) or may be of human origin (e.g. electronic devices). There are two types of electromagnetic radiation ionizing and non-ionizing and there are two types of non-ionizing radiation optical and radio-frequency.

These requirements deal with non-ionizing radiation and are divided into sections on optical (ultraviolet, infrared, and visible, including lasers) and radio-frequency (microwaves, radio-frequency, and extremely low frequency) radiation. Electromagnetic radiation may be considered as a series of waves of energy composed of oscillating electric and magnetic fields that travel through space until they are absorbed, reflected, transmitted and/or diffracted by objects in their path. The waves are characterized, in part, by the strengths of the electric and magnetic fields, the wavelength, and the frequency at which the waves oscillate.

Types of Ionizing Radiation

Alpha Particles

Some unstable atoms emit alpha particles (α). Alpha particles are positively charged and made up of two protons and two neutrons from the atom’s nucleus, as shown in the illustration at the right. Alpha particles come from the decay of the heaviest radioactive elements, such as uranium, radium and polonium. Even though alpha particles are very energetic, they are so heavy that they use up their energy over short distances and are unable to travel very far from the atom.

Beta Particles

Beta particles (β) are small, fast-moving particles with a negative electrical charge that are emitted from an β atom’s nucleus during radioactive decay. These particles are emitted by certa  in unstable atoms such as hydrogen-3 (tritium), carbon-14 and strontium-90. Beta particles are more penetrating than alpha particles but are less damaging to living tissue and DNA because the ionization they produce are more widely spaced. They travel farther in the air than alpha particles but can be stopped by a layer of clothing or by a thin layer of a substance such as aluminum.

Gamma Rays

Gamma rays (γ) are weightless packets of energy called photons. Unlike alpha and beta particles, which have both energy and mass, gamma rays are pure energy. Gamma rays are similar to visible light, but have much higher energy. Gamma rays are often emitted along with alpha or beta particles during radioactive decay.


Because of their use in medicine, almost everybody has heard of x-rays. X-rays are similar to gamma rays in that they are photons of pure energy. X-rays and gamma rays have the same basic properties but come from different parts of the atom. X-rays are emitted from processes outside the nucleus, but gamma rays originate inside the nucleus. They also are generally lower in energy and, therefore, less penetrating than gamma rays. X-rays can be produced naturally or artificially by machines using electricity.

Practise This Question

Two equal charges q of opposite sign separated by a distance 2a  constitute an electric dipole of dipole moment p . If P is a point at a distance r from the centre of the dipole and the line joining the centre of the dipole to this point makes an angle θ  with the axis of the dipole, then the potential at P is given by  (r >> 2a) (Where p = 2qa)