5.6 Uses of the electromagnetic spectrum
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Electromagnetic waves have many different uses. The use of electromagnetic waves is dependent upon the wavelength of the wave. In the next few pages, we will look at the uses of each type of electromagnetic waves.
The electromagnetic spectrum.
Radio Waves
Radio waves has the longest wavelength out of all the waves that we will look at. Their wavelengths are above 10 cm. Radio waves are used for TV remotes and FM radios. These have a length of around 10 cm to 10 m. To get reception, you must have direct sight of the transmitter as the small radio waves do not bend around hills.
Short-wave radio signals can be received at long distances from the transmitter. This is because they are reflected from the ionosphere. The ionosphere is an electrically charged layer of the earth’s upper atmosphere.
Long-wave radio can transmit information from the UK to the other side of the world because the radio waves bend and diffract around the earth’s surface. Long-wave radio waves have a wave length between 1 km and 10 km. They are also able to go inside tunnels. Long-wave radio waves are able to be received even if the radio signaller is not in site. This is due to diffraction.
Radio waves has the longest wavelength out of all the waves that we will look at. Their wavelengths are above 10 cm. Radio waves are used for TV remotes and FM radios. These have a length of around 10 cm to 10 m. To get reception, you must have direct sight of the transmitter as the small radio waves do not bend around hills.
Short-wave radio signals can be received at long distances from the transmitter. This is because they are reflected from the ionosphere. The ionosphere is an electrically charged layer of the earth’s upper atmosphere.
Long-wave radio can transmit information from the UK to the other side of the world because the radio waves bend and diffract around the earth’s surface. Long-wave radio waves have a wave length between 1 km and 10 km. They are also able to go inside tunnels. Long-wave radio waves are able to be received even if the radio signaller is not in site. This is due to diffraction.
Microwaves
Microwaves are used in communication from satellites. They are used for mobile phones and satellite TVs. Microwaves are used because the waves need to be able to pass through the earth’s watery atmosphere (which is the clouds and water vapour in the atmosphere).
Satellite TV works by a transmitter, transmitting the signal into space where it is received by a receiver dish on a satellite. The satellite then transmits the signal back to earth in a different direction where it is received by a satellite dish on the ground (such as a dish on the side of your house).
Mobile phones use microwaves. In order to save power and remain small, mobile phones send a message over a short range to the nearest mobile phone mast. Land is divided into many different cells with a mast in the centre of them. Some people believe that some of the waves that are sent out by a mobile phone are absorbed by water molecules in some of your cells. The microwaves then heat up the water in your cells and may pose some health risks. This would mean that speaking on the phone a lot or living next to a mobile phone mast could damage your health. However, there is no conclusive data that points to either of these stories being true.
Microwaves are used in communication from satellites. They are used for mobile phones and satellite TVs. Microwaves are used because the waves need to be able to pass through the earth’s watery atmosphere (which is the clouds and water vapour in the atmosphere).
Satellite TV works by a transmitter, transmitting the signal into space where it is received by a receiver dish on a satellite. The satellite then transmits the signal back to earth in a different direction where it is received by a satellite dish on the ground (such as a dish on the side of your house).
Mobile phones use microwaves. In order to save power and remain small, mobile phones send a message over a short range to the nearest mobile phone mast. Land is divided into many different cells with a mast in the centre of them. Some people believe that some of the waves that are sent out by a mobile phone are absorbed by water molecules in some of your cells. The microwaves then heat up the water in your cells and may pose some health risks. This would mean that speaking on the phone a lot or living next to a mobile phone mast could damage your health. However, there is no conclusive data that points to either of these stories being true.
Infrared Rays
Infrared waves are used in remotes, communication, night vision and heaters. Remotes use different patterns of infrared waves to send different instructions to a device. The change channel infrared frequency would be different to the increase volume infrared frequency. This allows the TV to understand what command it is you want it to do.
Night vision works by looking at the amount of infrared radiation given out by objects. The night vision camera would then turn infrared waves into a picture. Items that are giving out more infrared radiation will tend to be hotter and may be something of interest. For example, if we were in a forest looking for animals, we could use a night vision camera to see if there are any animals about and get a clear picture of the animals.
Infrared waves are used in remotes, communication, night vision and heaters. Remotes use different patterns of infrared waves to send different instructions to a device. The change channel infrared frequency would be different to the increase volume infrared frequency. This allows the TV to understand what command it is you want it to do.
Night vision works by looking at the amount of infrared radiation given out by objects. The night vision camera would then turn infrared waves into a picture. Items that are giving out more infrared radiation will tend to be hotter and may be something of interest. For example, if we were in a forest looking for animals, we could use a night vision camera to see if there are any animals about and get a clear picture of the animals.
Visible Light
Visible light is the only part of the electromagnetic spectrum that we can see.
Visible light and infrared waves are used in optical fibres. An optical fibre is a thin rod of high quality glass. Light goes into the glass at one end and it undergoes repeated total internal reflection, even when the fibre optic is bent. The light in the fibre optic never leaves the glass and is constantly reflected.
Information from computers or telephones can be converted into electrical waves and sent through fibre optic cables. Fibre optic cables are able to carry more information than ordinary cables of the same thickness. Also, they are able to keep the same quality of signal over very long distances. Sometimes the strength of the wave with ordinary cables weakens over longer distances.
Cameras use visible light. A lens is used to focus on visible light. We can then control the amount of light that is let into the camera by changing the aperture (size of the hole) and the shutter speed (the amount of time that the lens is open for). A film is then exposed to light and after development a picture is revealed.
Visible light is the only part of the electromagnetic spectrum that we can see.
Visible light and infrared waves are used in optical fibres. An optical fibre is a thin rod of high quality glass. Light goes into the glass at one end and it undergoes repeated total internal reflection, even when the fibre optic is bent. The light in the fibre optic never leaves the glass and is constantly reflected.
Information from computers or telephones can be converted into electrical waves and sent through fibre optic cables. Fibre optic cables are able to carry more information than ordinary cables of the same thickness. Also, they are able to keep the same quality of signal over very long distances. Sometimes the strength of the wave with ordinary cables weakens over longer distances.
Cameras use visible light. A lens is used to focus on visible light. We can then control the amount of light that is let into the camera by changing the aperture (size of the hole) and the shutter speed (the amount of time that the lens is open for). A film is then exposed to light and after development a picture is revealed.
Other Waves
The following electromagnetic waves are not needed for the exam but I think that it is nice to have some knowledge as to what each of the wave types is used for.
The following electromagnetic waves are not needed for the exam but I think that it is nice to have some knowledge as to what each of the wave types is used for.
- Ultraviolet Light: used in fluorescent lamps.
- X-rays: used in medical equipment to see internal structures of body parts. Some parts of the body absorb the X-ray waves (e.g. bones) and others let the waves pass through. This allows doctors and nurses to see bone structures and allows them to check if they are ok or not.
- Gamma Rays: used to sterilise food or hospital equipment. They are highly penetrative and kill microorganisms, hence making food and medical equipment safe.