![]() Even if the metal is exposed to such light for a long time, no emission of electrons is observed. Photons of low-frequency light do not contain enough energy to eject electrons from the metal. ![]() ![]() Since the electrons in the metal had a certain amount of binding energy keeping them there, the incident light needs to have more energy to free the electrons. This is also known as the work function ( W) of the metal. A certain minimum energy is required to overcome the binding energy (Φ) experienced by an electron. The photoelectric effect can be described by assuming that the light is quantized. The light striking the metal surface should not be viewed as a wave, but should instead be viewed as a stream of particles (later called photons) whose energy depended on their frequency, The amount of energy ( E) in a light packet depends on its frequency (ν) according to the following equation: In 1905, Albert Einstein was able to resolve the paradox by incorporating Planck's quantization findings into the discredited particle view of light.Įinstein argued that the quantized energies that Planck had postulated could be applied to the light in the photoelectric effect. One part of these observations was that the number of electrons ejected within a given time period was seen to increase as the brightness increased. ![]() However, when the frequency is higher than the threshold value, the number of electrons ejected is directly proportional to the intensity of the beam.Īccording to classical wave theory, a wave's energy depends on its intensity (which depends on its amplitude), not its frequency. Light with a frequency lower than the threshold frequency, even if it is of high intensity, cannot initiate the emission of electrons. The minimum frequency of light that can cause such emission of electrons is called the threshold frequency, which is specific to the metal. When light of a particular wavelength strikes a metal surface, electrons are emitted. ![]()
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