photons come out of a metal when it is hit by a beam of electrons

photons come out of the nucleus of an atom under the action of an electric field

electrons come out of a metal with a constant velocity which depends on the frequency and intensity of incident radiation

electrons come out of a metal with different velocities nor greater than a certain value which depends only on the frequency of the incident light and not on its intensity

light energy is converted into the heat energy

light is converted into electric energy

light energy is converted into the sound energy

electric energy is converted into light energy

the emission of electron is the result of elastic collision between the incident photon and the electron.

absorption of photon is a gradual process.

the emission of electron is a result of inelastic collision between the photon and the electron.

at the threshold frequency, the kinetic energy of ejected electrons is maximum.