1.2 Infrared Radiation
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Heat is also known as thermal energy. It can be transferred by infrared radiation, conduction or convection.
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Infrared Radiation
Heat can be transferred by infrared radiation. It can be absorbed and radiated by any object in all the three states (solids, liquids or gases). Infrared radiation is part of the electromagnetic spectrum. Infrared waves are longer than visible light and are a shorter length in comparison with microwaves. No particles are involved in radiation meaning that radiation works in a vacuum and this explains how we receive heat from the sun, despite the sun being 150 million km away.
The hotter an object is, the more infrared radiation will be emitted. If an object is hotter than its surroundings it will emit more infrared radiation than it is absorbing, thus meaning that the object will cool down. On the contrary, if an object is cooler than its surroundings, it will emit less radiation than it is receiving and will therefore heat up. The greater the temperature difference between an object and its surroundings, the faster energy is transferred. You can feel radiation if you standby something that is hotter than its surroundings, such as a radiator, kettle or an engine in a recently used car.
Infrared radiation levels depend on the surface colour and texture. Dark and matted surfaces absorb infrared radiation better than light shiny surfaces. Dark and matted surface also emit more radiation than light and shiny surfaces. Solar hot water panels are black because of dark surfaces absorb more infrared radiation and the more infrared radiation they absorb the hotter the water will be/ the water will get to the desired temperature faster. Light and shiny surfaces tend to reflect a lot of infrared radiation that falls on them. For example, a vacuum flask has a shiny inner surface to keep heat in or out.
The amount of radiation also depends on the shape of an object. If we had two objects with the same volume but they were different shapes; one thin and long object and the other fatter, the thin and long object would emit more infrared radiation that the fatter object. This is why radiators are thin and flat. Most radiators are painted with white gloss paint. They would emit more infrared radiation if they were painted with a matt paint instead (however, radiators transfer most of their heat through convection and conduction).
Heat can be transferred by infrared radiation. It can be absorbed and radiated by any object in all the three states (solids, liquids or gases). Infrared radiation is part of the electromagnetic spectrum. Infrared waves are longer than visible light and are a shorter length in comparison with microwaves. No particles are involved in radiation meaning that radiation works in a vacuum and this explains how we receive heat from the sun, despite the sun being 150 million km away.
The hotter an object is, the more infrared radiation will be emitted. If an object is hotter than its surroundings it will emit more infrared radiation than it is absorbing, thus meaning that the object will cool down. On the contrary, if an object is cooler than its surroundings, it will emit less radiation than it is receiving and will therefore heat up. The greater the temperature difference between an object and its surroundings, the faster energy is transferred. You can feel radiation if you standby something that is hotter than its surroundings, such as a radiator, kettle or an engine in a recently used car.
Infrared radiation levels depend on the surface colour and texture. Dark and matted surfaces absorb infrared radiation better than light shiny surfaces. Dark and matted surface also emit more radiation than light and shiny surfaces. Solar hot water panels are black because of dark surfaces absorb more infrared radiation and the more infrared radiation they absorb the hotter the water will be/ the water will get to the desired temperature faster. Light and shiny surfaces tend to reflect a lot of infrared radiation that falls on them. For example, a vacuum flask has a shiny inner surface to keep heat in or out.
The amount of radiation also depends on the shape of an object. If we had two objects with the same volume but they were different shapes; one thin and long object and the other fatter, the thin and long object would emit more infrared radiation that the fatter object. This is why radiators are thin and flat. Most radiators are painted with white gloss paint. They would emit more infrared radiation if they were painted with a matt paint instead (however, radiators transfer most of their heat through convection and conduction).