The energy of a photon is related to its frequency by where is Planck's constant, and so a spectrum of the system response vs. photon frequency will peak at the resonant frequency or energy.

This shift in photon frequency, known as the Brillouin shift, is equal to the energy of the interacting phonon or magnon and thus Brillouin scattering can be used to measure phonon or magnon energies.

However, a full microscopic computation generally produces that depends on both exciton index and photon frequency.

The three parameters , and , known as the Einstein coefficients, are associated with the photon frequency produced by the transition between two energy levels (states).

Chromatic dispersion in the radiator ( varies with photon frequency)

STJ devices have been employed as single-photon detectors for photon frequencies ranging from X-rays to the infrared.

In photonics band gaps or stop bands are ranges of photon frequencies where, if tunneling effects are neglected, no photons can be transmitted through a material.

Where is the two-photon absorption coefficient, is the absorption coefficient is the transition rate for TPA, is the irradiance, is the photon frequency and the thickness of the slice is .

It is just the low-energy limit of Compton scattering: the particle kinetic energy and photon frequency are the same before and after the scattering.

The important feature is that the cross section is independent of photon frequency.