Uses and dangers of electromagnetic radiation

What you'll learn

Why higher-frequency electromagnetic waves have greater potential danger.
The key harmful effects of excessive exposure to microwaves, infrared, ultraviolet, X-rays and gamma rays.
Common uses of each part of the electromagnetic spectrum.
How atoms, nuclei and electrical circuits can emit or absorb electromagnetic radiation.

The starting point: one spectrum

Definition

Electromagnetic radiation

Electromagnetic radiation is energy transferred by electromagnetic waves. These waves can travel through a vacuum, so they do not need particles to carry them.

The electromagnetic spectrum is a continuous range of waves. From lowest frequency to highest frequency, the order is:

radio waves → microwaves → infrared → visible light → ultraviolet → X-rays → gamma rays

Electromagnetic spectrum showing uses, dangers, increasing frequency and decreasing wavelength

Definition

Frequency and wavelength

Frequency $f$ is the number of complete waves passing a point each second, measured in hertz (Hz). Wavelength $λ\lambda$ is the distance from one point on a wave to the matching point on the next wave, measured in metres (m).

For waves, you can connect wave speed, frequency and wavelength using:

v=fλv=f\lambda

where $v$ is wave speed in metres per second (m/s). Electromagnetic waves in a vacuum all travel at about $3.0 \times 10^8 \text{ m/s}$ , so if frequency increases, wavelength decreases.

Key Idea

Frequency and potential danger

The potential danger of an electromagnetic wave increases as its frequency increases. This is why ultraviolet, X-rays and gamma rays need much more care than radio waves.

Common Mistake

Shorter wavelength means higher frequency

Do not say gamma rays have a long wavelength because they are “strong”. Gamma rays have very high frequency and very short wavelength.

Example

Comparing potential danger from wavelength

A microwave has wavelength $3.0 \times 10^{-2} \text{ m}$ . An ultraviolet wave has wavelength $3.0 \times 10^{-7} \text{ m}$ . Compare their potential dangers.

Calculate the ultraviolet frequency using $f=vλf=\frac{v}{\lambda}$ : $Hzf=\frac{3.0 \times 10^8 \text{ m/s}}{3.0 \times 10^{-7} \text{ m}}=1.0 \times 10^{15} \text{ Hz}$ .
Calculate the microwave frequency: $Hzf=\frac{3.0 \times 10^8 \text{ m/s}}{3.0 \times 10^{-2} \text{ m}}=1.0 \times 10^{10} \text{ Hz}$ .
Compare the frequencies: $1.0×10151.0×1010=1.0×105\frac{1.0 \times 10^{15}}{1.0 \times 10^{10}}=1.0 \times 10^5$ , so the ultraviolet has a much higher frequency and therefore greater potential danger.

Dangers of excessive exposure

Excessive exposure means being exposed to too much radiation, for too long, or without enough shielding. The effect depends on the type of radiation and how it interacts with body cells.

A mutation is a change to genetic material, such as DNA. Mutations can sometimes lead to cancer.

Radiation	Harmful effect of excessive exposure	What this means
Microwaves	Internal heating of body cells	Energy is absorbed inside the body, heating tissues.
Infrared	Skin burns	Infrared is strongly linked with heating surfaces.
Ultraviolet	Damage to surface cells and eyes	This can lead to skin cancer and eye conditions.
X-rays	Mutation or damage to cells in the body	X-rays can penetrate the body and damage internal cells.
Gamma rays	Mutation or damage to cells in the body	Gamma rays are very high frequency and highly penetrating.

Tip

Use the exact effect

In exam answers, “it is harmful” is usually too vague. Write the named effect, such as internal heating, skin burns, surface cell and eye damage, or cell mutation/damage.

Uses of electromagnetic radiation

Electromagnetic waves are useful because they can transfer energy, carry information, pass through some materials, or be detected by sensors.

Part of the spectrum	Uses you should know
Radio waves	Broadcasting, communications, satellite transmissions
Microwaves	Cooking, communications, satellite transmissions
Infrared	Cooking, thermal imaging, short-range communications, optical fibres, television remote controls, security systems
Visible light	Vision, photography, illumination
Ultraviolet	Security marking, fluorescent lamps, detecting forged bank notes, disinfecting water
X-rays	Observing the internal structure of objects, airport security scanners, medical X-rays
Gamma rays	Sterilising food and medical equipment, detecting cancer, treating cancer

Some uses are linked to a particular property. For example, infrared is emitted by warm objects, so it is useful for thermal imaging. X-rays pass through soft tissue more easily than bone or metal, so they can form images of internal structures.

A common swap to avoid: infrared is used for thermal imaging and TV remote controls, while ultraviolet is used for security marking, fluorescent lamps and detecting forged bank notes.

Example

Choosing radiation for internal imaging

A technician wants to see cracks inside a metal object without cutting it open. Which electromagnetic radiation could be used, and what safety issue matters?

The job requires radiation that can pass into the object and produce an image of internal structure, so ordinary visible light is not suitable.
X-rays are suitable because they are used for observing internal structures and in airport security scanners.
The safety issue is that X-rays can mutate or damage cells, so exposure should be controlled using shielding, reduced time and distance where appropriate.

Higher Tier link: radio waves and circuits

If you are taking Higher Tier, Edexcel can ask you to recall that radio waves can be produced by, or can themselves induce, oscillations in electrical circuits.

An oscillation is a repeated back-and-forth change. In a transmitting aerial, charges oscillate in a circuit and produce radio waves. In a receiving aerial, incoming radio waves can make charges oscillate, producing an electrical signal.

Here, induce means “cause to be produced” — the radio wave causes an oscillating current or voltage in the circuit.

Atoms and nuclei: absorbing and emitting radiation

An atom is the smallest part of an element that keeps that element’s properties. The nucleus is the tiny central part of an atom, containing protons and neutrons.

Changes in atoms and nuclei can generate electromagnetic radiation over a wide range of frequencies. For example, changes in atoms can produce visible light or ultraviolet, while changes in nuclei can produce gamma rays.

Radiation can also be absorbed, meaning its energy is taken in. Absorbing radiation can cause changes in atoms and nuclei. These changes might produce heating, fluorescence, ionisation, or cell damage depending on the radiation.

Definition

Ionising radiation

Ionising radiation has enough energy to remove electrons from atoms or molecules. X-rays and gamma rays are ionising, which is why they can damage cells and cause mutations.

Example

Explaining fluorescent security marking

A security mark is invisible in normal light but glows under ultraviolet.

The ultraviolet radiation is absorbed by atoms or molecules in the security ink, causing a change inside them.
As the atoms or molecules return to a lower-energy state, they emit visible light.
The visible glow reveals the mark, so it can be used to detect forged bank notes or check security markings.

Common Mistake

Radiation does not always mean radioactive

All parts of the electromagnetic spectrum are called radiation, but that does not mean every source is radioactive. Gamma rays are often produced by nuclear changes, but radio waves, infrared and visible light usually are not.

Exam technique

In the exam

Start by placing the wave in the spectrum: radio has low frequency; gamma has high frequency.
For danger questions, name the specific harmful effect and link it to excessive exposure.
For use questions, link the radiation to the job: for example, infrared for thermal imaging, ultraviolet for fluorescence, X-rays for internal imaging, gamma for sterilising or cancer treatment.

Self review

Check yourself

Why does the potential danger of electromagnetic radiation increase from radio waves towards gamma rays?
Give one use and one harmful effect of ultraviolet radiation.
How can radio waves be both produced by and detected by electrical circuits?

Uses and dangers of electromagnetic radiation

What you'll learn

Why higher-frequency electromagnetic waves have greater potential danger.
The key harmful effects of excessive exposure to microwaves, infrared, ultraviolet, X-rays and gamma rays.
Common uses of each part of the electromagnetic spectrum.
How atoms, nuclei and electrical circuits can emit or absorb electromagnetic radiation.

The starting point: one spectrum

Definition

Electromagnetic radiation

Electromagnetic radiation is energy transferred by electromagnetic waves. These waves can travel through a vacuum, so they do not need particles to carry them.

The electromagnetic spectrum is a continuous range of waves. From lowest frequency to highest frequency, the order is:

radio waves → microwaves → infrared → visible light → ultraviolet → X-rays → gamma rays

Electromagnetic spectrum showing uses, dangers, increasing frequency and decreasing wavelength

Definition

Frequency and wavelength

For waves, you can connect wave speed, frequency and wavelength using:

v=fλv=f\lambda

where $v$ is wave speed in metres per second (m/s). Electromagnetic waves in a vacuum all travel at about $3.0 \times 10^8 \text{ m/s}$ , so if frequency increases, wavelength decreases.

Key Idea

Frequency and potential danger

The potential danger of an electromagnetic wave increases as its frequency increases. This is why ultraviolet, X-rays and gamma rays need much more care than radio waves.

Common Mistake

Shorter wavelength means higher frequency

Do not say gamma rays have a long wavelength because they are “strong”. Gamma rays have very high frequency and very short wavelength.

Example

Comparing potential danger from wavelength

A microwave has wavelength $3.0 \times 10^{-2} \text{ m}$ . An ultraviolet wave has wavelength $3.0 \times 10^{-7} \text{ m}$ . Compare their potential dangers.

Calculate the ultraviolet frequency using $f=vλf=\frac{v}{\lambda}$ : $Hzf=\frac{3.0 \times 10^8 \text{ m/s}}{3.0 \times 10^{-7} \text{ m}}=1.0 \times 10^{15} \text{ Hz}$ .
Calculate the microwave frequency: $Hzf=\frac{3.0 \times 10^8 \text{ m/s}}{3.0 \times 10^{-2} \text{ m}}=1.0 \times 10^{10} \text{ Hz}$ .
Compare the frequencies: $1.0×10151.0×1010=1.0×105\frac{1.0 \times 10^{15}}{1.0 \times 10^{10}}=1.0 \times 10^5$ , so the ultraviolet has a much higher frequency and therefore greater potential danger.

Dangers of excessive exposure

Excessive exposure means being exposed to too much radiation, for too long, or without enough shielding. The effect depends on the type of radiation and how it interacts with body cells.

A mutation is a change to genetic material, such as DNA. Mutations can sometimes lead to cancer.

Radiation	Harmful effect of excessive exposure	What this means
Microwaves	Internal heating of body cells	Energy is absorbed inside the body, heating tissues.
Infrared	Skin burns	Infrared is strongly linked with heating surfaces.
Ultraviolet	Damage to surface cells and eyes	This can lead to skin cancer and eye conditions.
X-rays	Mutation or damage to cells in the body	X-rays can penetrate the body and damage internal cells.
Gamma rays	Mutation or damage to cells in the body	Gamma rays are very high frequency and highly penetrating.

Tip

Use the exact effect

In exam answers, “it is harmful” is usually too vague. Write the named effect, such as internal heating, skin burns, surface cell and eye damage, or cell mutation/damage.

Uses of electromagnetic radiation

Electromagnetic waves are useful because they can transfer energy, carry information, pass through some materials, or be detected by sensors.

Part of the spectrum	Uses you should know
Radio waves	Broadcasting, communications, satellite transmissions
Microwaves	Cooking, communications, satellite transmissions
Infrared	Cooking, thermal imaging, short-range communications, optical fibres, television remote controls, security systems
Visible light	Vision, photography, illumination
Ultraviolet	Security marking, fluorescent lamps, detecting forged bank notes, disinfecting water
X-rays	Observing the internal structure of objects, airport security scanners, medical X-rays
Gamma rays	Sterilising food and medical equipment, detecting cancer, treating cancer

A common swap to avoid: infrared is used for thermal imaging and TV remote controls, while ultraviolet is used for security marking, fluorescent lamps and detecting forged bank notes.

Example

Choosing radiation for internal imaging

A technician wants to see cracks inside a metal object without cutting it open. Which electromagnetic radiation could be used, and what safety issue matters?

The job requires radiation that can pass into the object and produce an image of internal structure, so ordinary visible light is not suitable.
X-rays are suitable because they are used for observing internal structures and in airport security scanners.
The safety issue is that X-rays can mutate or damage cells, so exposure should be controlled using shielding, reduced time and distance where appropriate.

Higher Tier link: radio waves and circuits

If you are taking Higher Tier, Edexcel can ask you to recall that radio waves can be produced by, or can themselves induce, oscillations in electrical circuits.

Here, induce means “cause to be produced” — the radio wave causes an oscillating current or voltage in the circuit.

Atoms and nuclei: absorbing and emitting radiation

An atom is the smallest part of an element that keeps that element’s properties. The nucleus is the tiny central part of an atom, containing protons and neutrons.

Definition

Ionising radiation

Ionising radiation has enough energy to remove electrons from atoms or molecules. X-rays and gamma rays are ionising, which is why they can damage cells and cause mutations.

Example

Explaining fluorescent security marking

A security mark is invisible in normal light but glows under ultraviolet.

The ultraviolet radiation is absorbed by atoms or molecules in the security ink, causing a change inside them.
As the atoms or molecules return to a lower-energy state, they emit visible light.
The visible glow reveals the mark, so it can be used to detect forged bank notes or check security markings.

Common Mistake

Radiation does not always mean radioactive

Exam technique

In the exam

Start by placing the wave in the spectrum: radio has low frequency; gamma has high frequency.
For danger questions, name the specific harmful effect and link it to excessive exposure.
For use questions, link the radiation to the job: for example, infrared for thermal imaging, ultraviolet for fluorescence, X-rays for internal imaging, gamma for sterilising or cancer treatment.

Self review

Check yourself

Why does the potential danger of electromagnetic radiation increase from radio waves towards gamma rays?
Give one use and one harmful effect of ultraviolet radiation.
How can radio waves be both produced by and detected by electrical circuits?

Uses and dangers of electromagnetic radiation

What you'll learn

The starting point: one spectrum

Dangers of excessive exposure

Uses of electromagnetic radiation

Higher Tier link: radio waves and circuits

Atoms and nuclei: absorbing and emitting radiation

Recap questions

You've reached the end

Uses and dangers of electromagnetic radiation

What you'll learn

The starting point: one spectrum

Dangers of excessive exposure

Uses of electromagnetic radiation

Higher Tier link: radio waves and circuits

Atoms and nuclei: absorbing and emitting radiation

Recap questions

You've reached the end

Uses and dangers of electromagnetic radiation

What you'll learn

The starting point: one spectrum

Dangers of excessive exposure

Uses of electromagnetic radiation

Higher Tier link: radio waves and circuits

Atoms and nuclei: absorbing and emitting radiation

Recap questions

You've reached the end

Uses and dangers of electromagnetic radiation Revision Guide

Uses and dangers of electromagnetic radiation

What you'll learn

The starting point: one spectrum

Dangers of excessive exposure

Uses of electromagnetic radiation

Higher Tier link: radio waves and circuits

Atoms and nuclei: absorbing and emitting radiation

Recap questions

You've reached the end

Uses and dangers of electromagnetic radiation Revision Guide