Question

What is photoelectric effect

Answer 1

It is the production of electrons or the free carriers when light is shone onto a material.
The electrons that are emitted in this manner can be called photoelectrons

Answer 2

The photoelectric effect or photoemission(given by Albert Einstein) is the production of electrons or other free carriers when light is shone onto a material. Electrons emitted in this manner can be called photoelectron's. The phenomenon is commonly studied in electronic physics, as well as in fields of chemistry, such as quantum chemistry or electro chemistry. According to classical electromagnetic theory, this effect can be attributed to the transfer of energy from the light to an electron. From this perspective, an alteration in the intensity of light would induce changes in the rate of emission of electrons from the metal. Furthermore, according to this theory, a sufficiently dim light would be expected to show a time lag between the initial shining of its light and the subsequent emission of an electron. However, the experimental results did not correlate with either of the two predictions made by classical theory. Instead, electrons are dislodged only by the impingement of photons when those photons reach or exceed a threshold frequency(energy). Below that threshold, no electrons are emitted from the metal regardless of the light intensity or the length of time of exposure to the light. To make sense of the fact that light can eject electrons even if its intensity is low,Albert Einstein proposed that a beam of light is not a wave propagating through space, but rather a collection of discrete wave packets(photons), each with energy of. This shed light on max Planck's previous discovery of the Planck relation(E=HF) linking energy (E) and frequency (f) as arising from quantization of energy. The fact or his known as the Planck constant.[1][2]In1887,Heinrich Hertz[2][3]discovered that electrodes illuminated with ultraviolet light create electric sparks more easily. In1905,Albert Einstein published a paper that explained experimental data from the photoelectric effect as the result of light energy being carried in discrete quantized packets. This discovery led to the quantum revolution. In 1914,Robert Millikan's experiment confirmed Einstein's law on photoelectric effect. Einstein was awarded the novel Prizein1921for "his discovery of the law of the photoelectric effect",[4]and Millikan was awarded the Nobel Prize in 1923 for "his work on the elementary charge of electricity and on the photoelectric effect".[5]The photoelectric effect requires photons with energies approaching zero (in the case of negative electron affinity) to over 1MeVfor core electrons in elements with a high atomic number. Emission of conduction electrons from typical metals usually requires a few electrons volts, corresponding to short I wavelength visible or ultraviolet light. Study of the photoelectric effect led to important steps in understanding the quantum nature of light and electrons and influenced the formation of the concept of waves particle duality.[1]Other phenomena where light affects the movement of electric charges include the photo conductive effect (also known as photo conductivity or photo resistivity), the photovoltaic effect, and the photo electrochemical effect. Photoemission can occur from any material, but it is most easily observable from metals or other conductors because the process produces a charge imbalance, and if this charge imbalance is not neutralized by current flow (enabled by conductivity), the potential barrier to emission increases until the emission current ceases. It is also usual to have the emitting surface in a vacuum, since gases impede the flow of photoelectron's and make them difficult to observe. Additionally, the energy barrier to photoemission is usually increased by thin oxide layers on metal surfaces if the metal has been exposed to oxygen, so most practical experiments and devices based on the photoelectric effect use clean metal surfaces in a vacuum. When the photoelectron is emitted into a solid rather than into a vacuum, the term internal photoemission is often used, and emission into a vacuum distinguished as external photoemission.