Waves

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Infrared Waves

All objects emit infrared radiation, how much depends on their temperature. We use IR to see objects in the dark, for heating and cooking, as well as communications.

This is the electromagnetic spectrum

Can you see where Gamma radiation, UV radiation, Infrared radiation and Microwave radiation sit on the spectrum?

So gamma rays have the highest frequency, then comes UV radiation, then infrared radiation, and microwave radiation has the lowest frequency out of the four types of light in the previous question.

What properties do infrared rays have?

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All objects give off infrared radiation. Do you think objects will radiate more if they are hot or cold?

How much infrared radiation an object will emit depends on its temperature. The hotter it is, the more it will radiate.

Which is best at emitting and absorbing radiation?

Out of these options, what do you think IR might be used for?

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Let's look more in detail at some of the uses of IR.

When infrared is absorbed by an object, the particles in the surface vibrate and gain kinetic energy. What do you think this might be useful for?

Grills and toasters use IR for cooking.

The surface of food gets hot and then the inside is heated by convection and conduction. However, this can be dangerous because the IR can also cause our skin to burn.

Infrared radiation is also used in remote controls for televisions and other electronic appliances.

The infrared signals produced cannot pass through solids, but they can get reflected off walls to operate the TV.

Because objects give off heat in the form of infrared radiation, we can use IR to see in the dark!

Night-vision goggles, cameras and thermograms use false colour so that we can "see" the radiation.

Infrared radiation can be used for communication as it can travel along glass optical fibres by being totally internally reflected.

The cladding of the fibres are made of a material which is more dense, so that it traps the rays in the core.

To sum up! Infrared radiation can be used for...

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