Black Body Radiation

Key Stage 4

Meaning

This is a graph of the black body radiation spectrum for several temperatures.

Black body radiation is the electromagnetic radiation given off by all objects with a temperature above absolute zero (0 Kelvin or -273°C).

About Black Body Radiation

All objects emit electromagnetic waves.

The frequency of electromagnetic wave depends upon the temperature of the object. The higher the temperature the higher the frequency of electromagnetic wave.

The Sun emits visible light because its temperature is so high.

Objects at room temperature emit Infra-red radiation. This can be seen using a thermal imaging camera.

The colour of an object affects the rate at which it absorbs or emits infra-red radiation. Dark colours both absorbs and emit infra-red radiation more quickly than light colours.

Reflective surfaces emit the least black body radiation.

When the rate of emission and absorption are the same then an object will remain at a constant temperature. If the rate of emission is greater than the rate of absorption then the object will decrease in temperature. If the rate of emission is less than the rate of absorption then the object will increase in temperature.