Different frequencies of electromagnetic radiation are used for different purposes due to their varying characteristics in reflection, absorption and transmission by various materials.
You should know the following examples:
X-rays
Chest X-ray
X-rays cannot be seen or felt. X-rays mostly pass through skin and soft tissue, but they do not easily pass through bone or metal. X-rays are used to produce shadow photographs of bones to check for damage such as fractures. They are also used in industry to check metal components and welds for cracks or other damage, and can detect objects hidden in the luggage of aircraft passengers.
Even low doses of X-rays can cause cells to become cancerous, so precautions are taken in hospitals to limit the dose received by patients and staff when X-ray photographs are taken.
Infrared radiation and visible light
Because these can travel long distances through glass without becoming significantly weaker, these are used in optical fibre communications.
Microwaves
Cooking
Microwave radiation has lower frequencies and longer wavelengths than visible light. Microwaves with certain wavelengths are absorbed by water molecules and can be used for cooking. Water in the food absorbs the microwave radiation, which causes the water to heat up and cook the food. The water in living cells can also absorb microwave radiation. As a result, they can be killed or damaged by the heat released.
Communications
A mobile phone mast - an example of a microwave transmitter
Microwave radiation can also be used to transmit signals such as mobile phone calls. Microwave transmitters and receivers on buildings and masts communicate with the mobile telephones in their range.
Certain microwave radiation wavelengths pass through the Earth's atmosphere and can be used to transmit information to and from satellites in orbit.
Metals reflect microwaves well. For this reason, satellite dishes are made from metal, and so are the cases of microwave ovens.
Radio waves
Radio waves are not strongly absorbed by the atmosphere so can be used to carry information for radio and TV programmes.
Different frequencies of electromagnetic radiation are used for different purposes due to their varying characteristics in reflection, absorption and transmission by various materials.You should know the following examples:X-raysChest X-rayX-rays cannot be seen or felt. X-rays mostly pass through skin and soft tissue, but they do not easily pass through bone or metal. X-rays are used to produce shadow photographs of bones to check for damage such as fractures. They are also used in industry to check metal components and welds for cracks or other damage, and can detect objects hidden in the luggage of aircraft passengers.Even low doses of X-rays can cause cells to become cancerous, so precautions are taken in hospitals to limit the dose received by patients and staff when X-ray photographs are taken.Infrared radiation and visible lightBecause these can travel long distances through glass without becoming significantly weaker, these are used in optical fibre communications.MicrowavesCookingMicrowave radiation has lower frequencies and longer wavelengths than visible light. Microwaves with certain wavelengths are absorbed by water molecules and can be used for cooking. Water in the food absorbs the microwave radiation, which causes the water to heat up and cook the food. The water in living cells can also absorb microwave radiation. As a result, they can be killed or damaged by the heat released.CommunicationsA mobile phone mast - an example of a microwave transmitterMicrowave radiation can also be used to transmit signals such as mobile phone calls. Microwave transmitters and receivers on buildings and masts communicate with the mobile telephones in their range.Certain microwave radiation wavelengths pass through the Earth's atmosphere and can be used to transmit information to and from satellites in orbit.Metals reflect microwaves well. For this reason, satellite dishes are made from metal, and so are the cases of microwave ovens.Radio wavesRadio waves are not strongly absorbed by the atmosphere so can be used to carry information for radio and TV programmes.
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