Transmission of heat

The global greenhouse effect

The global greenhouse effect The earth’s atmosphere behaves like a greenhouse. The sun’s radiation easily passes through it and is absorbed by the earth’s surfaces. As it warms up, the earth re-radiates energy of longer wavelengths. This becomes absorbed by water vapour, carbon .dioxide and other gases in the atmosphere. The warm atmosphere, in turn, radiates back to the …

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The greenhouse

The greenhouse Anyone who walks into a greenhouse, even on a day when the sunlight is rather dull, realizes how efficiently it acts as a radiation trap. Very hot bodies such as the sun emit most of their radiation in the form of visible light and short wavelength infrared rays which easily pass through glass without being absorbed. (The …

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Practical applications of radiation

Practical applications of radiation The investigations on radiation and absorption described above have a umber of useful applications. Buildings which are whitewashed or painted in light  olours keep cooler in summer, since the light surfaces reflect ‘radiation from the sun. Many factory roofs are now aluminium-painted. The bright surface reduces the heat lost in winter, and keeps the interior …

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RADIATION

RADIATION Both conduction and convection are ways of conveying heat from one place to another which require the presence of a material substance, either solid, liquid, or gas. There is a third process of heat transmission which does not require a material medium. This is called radiation, and is the means by which energy travels from the sun across …

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