# property>second radiation constant

## What is the Second Radiation Constant?

The second radiation constant, c_{2}, is used in Planck's law. It has the SI units of metres kelvin. It is given by the equation:

c_{2} = hc / k

where h is the Planck constant, c is the speed of light and k is the Boltzmann constant. Its value is 1.438775x10^{-2} m K.

Planck's law gives the radiation intensity emitted by a black body for a given frequency and temperature. It has the form:

u = c_{1}.λ^{-5} / (ε^{c2/λT} - 1)