GCSE Physics · Edexcel 1PH0 · Topic 5D
Radiation and temperature
Key points
- All objects emit and absorb infrared radiation, whatever their temperature.
- The hotter an object, the more radiation it emits per second and the shorter the wavelength of the peak; very hot objects glow red then white.
- An object at constant temperature absorbs radiation at the same rate as it emits it.
- If it absorbs more than it emits, its temperature rises; if it emits more, it cools.
- Matt black surfaces are the best absorbers and emitters; shiny, light surfaces are the poorest and best reflectors (tested with a Leslie cube).
- Earth's temperature depends on the balance of absorbed sunlight and emitted infrared; greenhouse gases absorb some outgoing radiation.
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Every object, from an ice cube to the Sun, gives out electromagnetic radiation. This sub-topic explains how the amount and type of radiation depend on temperature, and how a balance between absorbing and emitting sets the temperature of…
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