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Energy Transfer

How is Heat Radiation (Infra-red Radiation) Transferred?

Infra-red radiation (also called thermal radiation)
transfers heat between all objects. The frequency at which
an object emits electromagnetic radiation is called
its principle frequency. The principle frequency increases
as the temperature increases. The Sun is hotter than
the Earth and so has a higher principle frequency.
Infra-red radiation is an electromagnetic wave and can travel
through a vacuum. Heat from the Sun reaches us through
the vacuum of space by travelling as infra-red radiation.

An object can absorb radiation (take it in),
emit radiation (give it out) and reflect radiation.

The hotter an object, the faster it will emit infra-red radiation.
Hotter objects will emit infra-red radiation faster
than they absorb it from colder objects around them.
Colder objects will absorb infra-red radiation
than they emit it to hotter objects around them.
In this way heat is transferred from hotter to colder objects.
An object whose temperature does not change
emits infra-red radiation at the same rate as it is absorbed.

Objects that are at the same temperature as each other
absorb, emit and reflect infra-red radiation at different rates
depending on the type of surface that the object has.

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