Magnetism and magnetic fields Study Guide

Radioactive decay is the process by which an unstable atomic nucleus loses energy by emitting radiation. This emission causes fundamental changes to the nucleus, affecting both its mass (nucleon number) and its charge (proton number). There are four main types of emissions: alpha particles, beta particles, gamma rays, and neutrons.

An alpha particle consists of two protons and two neutrons, identical to a helium nucleus. When a nucleus emits an alpha particle, its proton number decreases by 2, and its nucleon number decreases by 4. This significantly alters the element, as the proton number defines the element.

A beta particle is a high-energy electron emitted from the nucleus when a neutron transforms into a proton, releasing an electron and an antineutrino. This process increases the proton number by 1, but the nucleon number remains unchanged (a neutron is replaced by a proton). This also changes the identity of the element.

Gamma radiation consists of high-energy electromagnetic waves. Unlike alpha and beta decay, gamma emission does not involve particles with mass or charge. Therefore, when a nucleus emits a gamma ray, its proton number and nucleon number remain unchanged. Gamma emission often accompanies alpha or beta decay as the nucleus releases excess energy and settles into a more stable state.

Neutrons are uncharged subatomic particles found in the nucleus. The emission of a neutron means the proton number of the nucleus remains the same, but the nucleon number decreases by 1. This results in an isotope of the original element being formed, as the number of protons (and thus the element) has not changed, only the number of neutrons.

The electromagnetic (EM) spectrum is a continuous range of waves that travel at the speed of light in a vacuum. These waves are oscillations of electric and magnetic fields and do not require a medium to travel, meaning they can travel through space. The EM spectrum is categorised by wavelength and frequency into seven main regions: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. Each region has distinct properties that make it suitable for various practical applications.

Radio waves have the longest wavelengths and lowest frequencies. Their ability to travel long distances and pass through obstacles makes them ideal for communication technologies such as radio broadcasting, television, and mobile phone signals. Microwaves have shorter wavelengths than radio waves and are used in microwave ovens to heat food by causing water molecules to vibrate. They are also essential for satellite communication and radar systems.

Infrared radiation is associated with heat. Remote controls for televisions, night vision cameras, and thermal imaging use infrared. Visible light is the only part of the spectrum that humans can see, enabling us to perceive colour and form. It is fundamental for everyday tasks, photography, and fibre optic communication.

Ultraviolet (UV) radiation has shorter wavelengths and higher frequencies than visible light. It is used in sunbeds, sterilisation of medical equipment, and security marking for banknotes. Excessive exposure can be harmful. X-rays are even more energetic and can penetrate soft tissues, making them invaluable for medical imaging to detect fractures and in airport security scanners. Gamma rays, at the highest energy end of the spectrum, are produced by radioactive decay and nuclear processes. They are used in radiotherapy to treat cancer, sterilise medical instruments, and preserve food by killing microorganisms.