The antiparticle of an electron is:

The frequency of a photon having energy $66 \ eV$ is:

There are materials which absorb photons of shorter wavelength and emit photons of longer wavelength. Can there be stable substances which absorb photons of larger wavelength and emit light of shorter wavelength?

According to the photon theory of light,which of the following physical quantities associated with a photon does not change as it collides with an electron in a vacuum?

The energy of a photon of wavelength $\lambda$ is given by

The idea of the quantum nature of light has emerged in an attempt to explain: