Chapter 3: Unit 3. Different types of Radiation

Different Types of Radiation

A radioactive nucleus can emit α (alpha) particle, β (beta) -particles, positron or γ (gamma) rays.

An α particle is high energy nucleus that contains two protons and two neutrons, symbolized as ⁴₂He

A β particle is equivalent to high energy electron, can be symbolized as ⁰_-1e.

A positron is an antiparticle of a beta particle. A positron has +1 charge and negligible mass( β⁺).

A gamma ray is high energy radiation with no mass and charge. Symbol of γ ray is ⁰₀γ.

Below is the diagram where radioactive substances inside a lead block emit radiation and how they behave differently when electrical field is applied to the radiations.

An alpha particle, because it’s very heavy and has a very large charge, doesn’t go very far at all. This means an alpha particle can’t even get through a sheet of paper. An alpha particle outside your body won’t even penetrate the surface of your skin. But, if you inhale or ingest material that emits alpha particles, sensitive tissue like the lungs can be exposed. This is why high levels of radon are considered a problem in your home. The ability to stop alpha particles so easily is useful in smoke detectors, because a little smoke in the chamber is enough to stop the alpha particle and trigger the alarm.

Beta particles go a little farther than alpha particles. You could use a relatively small amount of shielding to stop them. They can get into your body but can’t go all the way through. To be useful in medical imaging, beta particles must be released by a material that is injected into the body. They can also be very useful in cancer therapy if you can put the radioactive material in a tumor.

Gamma rays and x-rays can penetrate through the body. This is why they are useful in medicine—to show whether bones are broken or where there is tooth decay, or to locate a tumor. Shielding with dense materials like concrete and lead is used to avoid exposing sensitive internal organs or the people who may be working with this type of radiation. For example, the technician who does my dental x-rays puts a lead apron over me before taking the picture. That apron stops the x-rays from getting to the rest of my body. The technician stands behind the wall, which usually has some lead in it, to protect him or herself.

Radiation is all around us (called background radiation), but that is not a reason to be afraid. Different types of radiation behave differently, and some forms can be very useful.  The diagram below shows the penetrating power of different types of radiations.

Summary of all types of radiations:

Here is the summary of characteristics of all three types of radiation

Watch the following video:

Questions:

1. Identify the type of radiation in following symbols of radiation (S):a) ⁰_-1S b) ⁴₂S c) ⁰₊₁S

2. Which nuclear emission has greatest mass and least penetrating power?

Ans: 1. a)

1. b) alpha
2. c) positron

2. Alpha