The electron volt (eV) is a unit of energy equal to approximately 1.6×10?19 joule (J). By definition, it is the amount of energy gained (or lost) by the charge of a single electron moved across an electric potential difference of one volt. read more
yes, if it gained energy from a collision with the electron. for photon wavelength to decrease its frequency will increase and energy will increase. so the photon must gain energy from the collision with the electron. read more