Yes, the equation E = hf, where E represents energy, h is the Planck constant, and f represents the frequency, is applicable to particles other than photons as well. This equation is a fundamental relation in quantum mechanics known as the energy-momentum relation.
In the context of photons, which are particles of light, the equation E = hf relates the energy of a photon to its frequency. The energy of a photon is directly proportional to its frequency, where the constant of proportionality is the Planck constant.
However, the energy-momentum relation extends beyond photons and applies to other particles as well, including elementary particles such as electrons, protons, neutrons, and other particles with mass. For particles with mass, the equation is generalized to E^2 = (mc^2)^2 + (pc)^2, where m represents the mass, c is the speed of light, p is the momentum of the particle, and E is the total energy.
For particles with mass, the equation takes into account both the rest mass energy (mc^2) and the energy associated with the particle's momentum. The momentum of a particle is related to its wavelength through the de Broglie relation, p = h/λ, where λ represents the wavelength. Therefore, the energy-momentum relation for particles with mass incorporates both the rest mass energy and the energy associated with their momentum.
In summary, while the equation E = hf is specifically applicable to photons, the energy-momentum relation is a more general concept that applies to particles with and without mass, taking into account both their rest mass energy and their momentum.