One topic covered in GCSE Science is the transfer of heat (thermal) energy. This is one of eight quizzes on that subject and it looks specifically at infrared radiation.
Infrared radiation is a part of the electromagnetic spectrum. This is a spectrum of waves that also includes light. Infrared is also called thermal radiation and is one way in which heat is transferred. Infrared is emitted (given off), absorbed (taken in) and reflected by all objects. Hotter objects give out more infrared radiation than cooler ones. It has a wavelength of just a little longer than red light waves - you may have seen or done an experiment yourself using a thermometer, prism and light source. When the visible light is dispersed (split into the colours of the rainbow) by the prism, if you hold the thermometer just beyond where the red is, the reading will increase slightly.
Since infrared is an electromagnetic wave, unlike conduction and convection, it does not require any particles to transfer it. Space is the ultimate insulator and there are too few particles in space to allow convection. Despite this, heat still reaches the Earth from the Sun. That is because it arrives in the form of infrared radiation and space is mainly transparent.
Infrared can easily be blocked. You can try this for yourself. On a sunny day, hold a piece of paper between the back of your hand and the Sun. Your hand will feel immediately cooler when the paper is casting a shadow. As well as being blocked, infrared is easily absorbed. However, some colours and surfaces absorb, emit and reflect infrared more efficiently than others. You will have learnt these in your lessons and will be expected to know them for the exam.
Infrared radiation is invisible to our eyes, but if there is enough, we can detect it with our skin as heat. Infrared sensors can detect heat from the body. They are used in security lights, burglar alarms and to automatically switch lighting on and off when someone enters or leaves a room. Thermal radiation is also used to transmit information from place to place, including remote controls for television sets, DVD players and similar appliances as well as for data links over short distances between computers or mobile phones.
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