RADIATION
The transfer of heat energy from a hot body to a cold body directly, without heating the space in between the two bodies is called radiation.
When we sit in the sun or in front of a heater, we feel warmth. Heat energy reaches us by radiation. This heat cannot reach us by conduction because air is a bad conductor of heat. Similarly, this heat cannot reach us by convection, as the hot air rises upward, rather than sideways. If we put a cardboard or a plastic sheet between us and the source of heat, we no longer feel warmth. So, we can say that heat from the Sun or a heater reaches us by radiation which requires no medium as shown in this diagram.
Experiments on Radiation and Absorption
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