Radiation: Types, Effects & Applications in Physics

Radiation: The types, principles, effects and applications

Introduction

Radiation refers to the outlay and transmission of energy in space or matter in the form of waves or particles. It is a natural physical fact that is the key to nature, technology, medicine, and industry. Radiation is everywhere in the modern world; from sunlight that warms the earth to medical imaging and nuclear power, it has found its place in life. The study of radiation entails the study of its types, sources, physical laws, its measurement, biological effects, as well as its practical applications.

What Is Radiation?

Radiation is considered to be the transfer of energy between two points without necessarily using a physical medium (electromagnetic radiation) or by using moving particles (particle radiation). This can be categorized into two broad categories:

Electromagnetic radiation
Particle radiation

Ionising and non-ionising Radiation may also be categorised as either ionising or non-ionising in terms of their capacity to take away electrons in atoms.

Electromagnetic Radiation

The Electromagnetic (EM) radiation is a combination of vibrating electromagnetic and electric fields travelling at the speed of light in space:

c = 3.0 × 10⁸ ms–1

Examples include:

Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays

EM radiations are governed by the equation of a wave:

c = f λ

where:

c = speed of light
f = frequency
λ = wavelength

Energy of a photon is given by:

E = h f

where:

E = energy
h = Planck's constant (6.63 × 10³⁴, J s )
f = frequency

An increase in frequency implies an increase in energy. In this way, gamma rays are much more powerful than radio waves.

Particle Radiation

Particle radiation entails subatomic particles travelling rapidly and emitted by unstable atomic nuclei. The main types are:

Alpha (α) Radiation

Has helium nuclei (2 protons + 2 neutrons) as its components. It is massive and up-charged.
Low penetration arrested by paper or skin.
Strong ionising ability

Beta (β) Radiation

Rapid electrons (b-), or positrons (b+).
Faster and lighter than alpha particles.
Moderate penetration- interrupted by aluminium sheets.
Moderate ionising ability

Gamma Radiation

The nuclear transitions are high-energy electromagnetic waves.
Brutally penetrating - needs heavy lead or concrete armour.
Weakly ionising per interaction, but harmful because of deep penetration

Radioactive Decay

Radioactive decay takes place when unstable nuclei give out radiation in order to become more stable. This follows a random and yet predictable process.

Following the number of undecayed nuclei:

N = N₀e^{– λt}

where:

N = remaining nuclei
N₀ = initial nuclei
λ = decay constant
t = time

Half-Life

The half-life of the nuclei is the period required to decay half of the nuclei:

T_½ = ln 2/λ

The half-life is not very constant - it can be as short as a few seconds and as long as several billion years.

Measurement of Radiation

The measurement of radiation is done in various units depending on the circumstance.

Activity

Measures decay rate:

Measure: becquerel (Bq) = -1 seconds.

Absorbed Dose

Energy taken up/unit mass:

Unit: gray (Gy)

1Gy = 1J kg ^–1

Equivalent Dose

Explanations of biological effect:

H = D× ω_R

ω_R is the radiation weighting factor.

Unit: sievert (Sv)

Interaction with Matter

Radiation may interact with matter in several ways:

Ionisation

Radiation causes the loss of electrons in atoms, creating ions.

Excitation

The electrons are elevated to elevated energy levels with no elimination.

Attenuation

There is a decrease in intensity with the thickness:

I = I₀e^–μx

where:

I = transmitted intensity
I₀= original intensity
μ = attenuation coefficient
x = thickness

This is applied in the design of shielding.

Biological Effects of Radiation

Radiation can impact living tissue by destroying molecules, especially DNA.

Types of Effects

Deterministic effects

It occurs above a threshold dose. The dose is proportional to the severity.
Examples: radiation sickness, burns.

Stochastic effects

There is no threshold. The dose-response is positive.
Examples: genetic mutations, cancer.

Radiation Sickness

Develops following acute exposure to a high degree:

Nausea
Fatigue
Hair loss
Immune suppression
Organ damage

Radiation Protection

There are three key principles, which minimise exposure:

Time

Reduce exposure duration.

Distance

Intensity obeys an inverse square law:

The doubling of the distance is four times less.

Shielding

Use absorbing materials:

Paper -- alpha
Aluminium -- beta
Lead/concrete - X-ray and gamma.

Applications

Medical Applications

X-ray imaging - This involves penetration radiation which is used to create images of bones and hard tissues.

Industrial Applications

Non-destructive testing - This is done on metals and welds that are not cut.

Energy Production

Nuclear power generation- This is a method of electricity generation done by controlled nuclear fission.

Scientific Research

Radiometric dating -Determines the age of archaeological and geological samples.

Space and Exploration

Spacecraft power systems - radioactive sources on long-duration missions.

Conclusion

Radiation is an extremely strong and versatile natural phenomenon that forms the basis of a large portion of modern science and technology. It can occur in numerous forms, radio waves that are harmless and gamma rays, which are very energetic. Although ionising radiations are health hazards, with the right kind of measurements, control and protective measures, they can be used safely and effectively in medicine, industry, research and energy generation. A sound knowledge of radiation physics, such as decay laws, principles of interaction and principles of protection, is needed to deal with its advantages and dangers.

FAQs

What is background radiation?

Background radiation refers to the low level of radiation that is present in the environment at all times due to natural causes, e.g., cosmic rays, radon gas, and naturally occurring isotopes.