Uses of electromagnetic waves

In a nutshell

The different types of electromagnetic waves have different uses. There are also dangers of EM waves when using the higher frequency radiation types.

Uses of radiation

Type	Uses	Examples
Radio waves	Communication	Radio broadcasting from radio towers
Microwaves	Communication & heating	Microwaves to heat food
Infrared radiation	Heating	Infrared cameras & electric heaters
Visible light	Light & communication	Fibre optic cables in HD Television
Ultraviolet radiation	Light & security	Fluorescent lights & checking counterfeit money
X-rays	Medicine	X-ray photography & cancer treatment
Gamma rays	Medicine	Radiotherapy & medical tracers

Uses of each electromagnetic wave

Electromagnetic waves have different uses depending on their frequency. This is because they have different characteristic and behaviours.

Radio waves

Radio waves are mostly used for communication as they can travel through the Earth's atmosphere. Long wavelengths easily bend around the Earth so they can be used to send information over large distances. They are able to be reflected and do not cause harm to human body tissue.

Example

Radio broadcasting uses radio waves sent out by radio towers.

For Higher Spec Only:

EM waves can be generated using an alternating current and a transmitter. This is because a current consists of oscillating charges. These charges produce oscillating electric and magnetic fields - electromagnetic waves. The frequency of the waves generated will be the same as the frequency of the alternating current used.

When radio waves are absorbed by a receiver they generate an alternating current of the same frequency as the waves. This makes them useful for sending signals.

Microwaves

Microwaves are also used for communication, specifically with satellites. Microwaves can pass out of Earth's atmosphere. They are received by satellites and transmitted back to Earth.

They are also used for heating food. The higher frequencies of microwave can be absorbed by food. The energy is transferred to the internal energy (kinetic + potential energy) of the food molecules. This causes the food to heat up.

Example

A microwave unsurprisingly uses microwaves! These are higher frequencies of microwave which can be used to heat food.

Curiosity: Yes, microwaves aren't just for heating food! Microwaves have many uses as only the small range used for heating food is harmful to humans.

Infrared (IR)

Any hot object gives off infrared radiation - the hotter it is, the more radiation it gives off. It can also be used for cooking as absorbing IR radiation heats up the object.

Example

Infrared cameras are used to monitor temperatures by converting the IR radiation to electrical signals.

Electric heaters emit IR radiation to heat rooms.

Visible light

The main use of visible light is to see! It is also used in fibre optic cables. Fibre optic cables are thin glass fibres that carry data over long distances. This works due to light being reflected until it is passed down the length of the cable.

Example

HD Television uses fibre optic cables as they are able to transmit information quickly.

Ultraviolet (UV)

Fluorescence occurs when ultraviolet radiation is absorbed by an object and visible light it emitted. Fluorescent lights emit UV radiation which is absorbed by a thin layer of phosphorus in the bulb. This layer then emits visible light.

The Sun produces UV radiation. When the body is exposed to this it tans. Tanning can lead to skin cancer, as prolonged exposure to UV radiation can have hazardous effects to the body.

Example

UV radiation is used to check counterfeit (fake) money for security purposes.

X-rays

X-Rays can be used by radiographers to take photos of bones. This is because the rays can pass easily through human flesh but are stopped by bones.

They can also be used to treat cancer as high doses can kill living cells. This has to be done carefully to avoid killing too many healthy cells.

Example

Hospitals use X-Ray photography to find out if bones are broken. The 'shadow' of the X-rays create a photo.

Gamma rays

Gamma rays are also used to treat cancer using the same method as X-rays. Gamma radiation can also be used as medical tracers which are injected into the body. Its progress around the body can be tracked and analysed.

Example

Hospitals use gamma radiation in radiotherapy to kill cancer cells and shrink tumours.

Dangers of radiation

High frequency waves transfer a lot of energy. This can cause damage if absorbed by living tissue. UV radiation harms surface cells, which can cause blindness or skin cancer.

X-rays and gamma rays have high ionising power which can cause cell destruction and cancer. Protective measures, such as wearing a lead apron or reducing contact, have to be taken to minimise risk.

Radiation dose is a measure of the risk from exposure to radiation. It is measured in sieverts ( $Sv$ ).

Tip: You don't need to know sieverts for the topic, but they will come up again in 'Radioactivity'!