⇒ Radio waves are used to transmit both radio signals and terrestrial TV signals

• Terrestrial television is a type of television broadcasting in which the television signal is transmitted by radio waves from the terrestrial (Earth-based) transmitter of a television station to a TV receiver having an antenna.

⇒ Radio waves are used because they travel long distances before being absorbed e.g. by building and trees

⇒ Longer wavelength radio waves can also spread out between hills (this is called diffraction)

⇒ Radio waves can also reflect off a layer of charged particles in the atmosphere (the ionosphere)

• This allows us to send radio waves very long distances around the world

⇒ Microwaves are used for heating food - that is because most foods contain a lot of water molecules, which absorb the energy of microwaves

⇒ The energy causes the temperature of the food to increase

⇒ Microwaves are also used to communicate with satellites in space

• That is because microwaves can pass through the Earth's atmosphere without being reflected or refracted

⇒ Infrared is emitted by electrical heaters and is also used to cook food in ovens

⇒ That is because the energy of infrared is easily absorbed by the surface of objects

⇒ The infrared from the heater is absorbed by objects in the room and this makes the room warmer

⇒ Infrared is also used in infrared cameras, which can check buildings for heat loss

⇒ A really important use of visible light is communication using fibre optics

⇒ This shows a bunch of optical fibres - optical fibres are very thin strands of glass

⇒ We can transmit pulses of light down these fibres and use these pulses to carry informtion

⇒ Optical fibres are used to carry telephone and cable TV signals

⇒ Because visible light has a short wavelength, it can carry a great deal of information

⇒ A really important use of ultraviolet is in energy efficient lightbulbs

⇒ Ultraviolet light is created inside the bulb

⇒ Because ultraviolet has a short wavelength, it carries more energy than visible light

⇒ The energy of the ultraviolet is absorbed by the internal surface of the bulb and it is convered to visible light

• This requires much less energy than a normal bulb

⇒ Another use of ultraviolet is in sun tanning e.g. using a tanning bed

• Remember that ultraviolet increases the risk of skin cancer and causes premature skin ageing

⇒ Both X rays and gamma rays are used for medical imaging

⇒ X-rays can be used to visualise broken bones

⇒ Gamma rays are used to detect cancers

⇒ Both x rays and gamma rays are very penetrative, meaning they can easily pass through body tissue

⇒ X-Rays are absorbed by bones, which is why we can see them on X-ray images

⇒ Both x-rays and gamma rays can also be used in medical treatments e.g. to treat cancer

⇒ Also see our notes on:

• Electric Current
• Current, Voltage and Resistance
• The Dynamo Effect
• Power Stations
• Electrical Power
• Waves - The Basics
• Waves
• Refraction
• Em Radiation
• Analogue and Digital Signals
• Wind and Solar Energy
• Seismic Waves