# Spectral Exitance (real surface)

## Description

The spectral exitance of a real surface around a given frequency or wavelength, according to the Lambert’s cosine law and the Planck’s law, is equal to the formula shown here.

Related formulas## Variables

M_{e}λ | spectral exitance (watt/m^{3}) |

π | pi |

h | Planck constant |

c | Speed of light |

λ | wavelength (m) |

e | e |

k | Boltzmann constant |

T | temperature of that surface (K) |