Topic 5.22: Uses of electromagnetic radiation

What are radio waves used for?

Broadcasting, communications and satellite transmissions.

How are radio waves used in broadcasting?

They carry information in radio and television signals.

How can radio waves be used in communications?

They transmit information wirelessly over long distances.

What are microwaves used for?

Cooking, communications and satellite transmissions.

How do microwave ovens heat food?

Microwaves are absorbed by water and other molecules in food, transferring energy and heating it.

Why are microwaves suitable for satellite communications?

They can pass through the atmosphere in suitable frequency bands and carry large amounts of information.

What are infrared waves used for?

Cooking, thermal imaging, short-range communications, optical fibres, television remote controls and security systems.

How does a thermal imaging camera use infrared radiation?

It detects infrared radiation emitted by objects and produces an image showing temperature differences.

How are infrared waves used in television remote controls?

The remote sends coded infrared pulses to a receiver in the television.

How can infrared radiation be used in security systems?

Infrared sensors detect emitted radiation or changes in infrared signals.

How is infrared used in optical fibres?

Infrared signals can carry information through optical fibres over long distances.

What is visible light used for?

Vision, photography and illumination.

How does a camera use visible light?

A lens focuses light onto a sensor or film to record an image.

What are ultraviolet waves used for?

Security marking, fluorescent lamps, detecting forged banknotes and disinfecting water.

How can ultraviolet radiation detect forged banknotes?

Security features fluoresce under ultraviolet light.

How can ultraviolet radiation disinfect water?

UV radiation damages the genetic material of microorganisms, preventing them from reproducing.

How do fluorescent lamps use ultraviolet radiation?

An electrical discharge produces UV radiation, which causes a coating inside the lamp to emit visible light.

What are X-rays used for?

Medical imaging, observing internal structures and airport security scanners.

How do medical X-rays produce images?

Different tissues absorb X-rays by different amounts, creating contrast on a detector.

Why do bones appear clearly on X-ray images?

Bones absorb more X-rays than many surrounding soft tissues.

How are X-rays used in airport security?

They pass through luggage and are absorbed differently by different materials, helping reveal hidden objects.

What are gamma rays used for?

Sterilising food and medical equipment, detecting cancer and treating cancer.

How are gamma rays used to sterilise medical equipment?

They kill microorganisms by damaging their cells and genetic material.

How can gamma rays be used to treat cancer?

They are directed at cancerous tissue to damage and destroy cancer cells.

How can electromagnetic radiation be used to detect cancer?

Imaging techniques using suitable electromagnetic radiation can reveal abnormalities; gamma-emitting tracers may be used in nuclear medicine.

What determines which electromagnetic wave is selected for a particular use?

Factors such as wavelength, frequency, energy, penetration, absorption and the information to be transmitted.