In 1887, German scientist Hertz discovered the influence of light on the electrical discharge.Studying spark Hertz discovered that if a negative electrode illuminate with ultraviolet rays, the discharge occurs at a lower voltage on the electrodes.
further been found that when illuminated electric arc negatively charged metal plate connected to the electroscope arrow electroscope falls.This indicated that the illuminated arc metal plate loses its negative charge.The positive charge of the metal plate is illuminated loses.
Loss metal bodies when illuminated by light rays negative electric charge is called the photoelectric effect, or simply the photoelectric effect.
physics of this phenomenon has been studied since 1888 and the famous Russian scientist AG Stoletov.
study of the photoelectric effect centuries was made by setting consisting of two small discs.Solid zinc plate and fine mesh installed vertically against each other, forming a capacitor.Its plate connected with the poles of the current source, and then illuminated with light of an electric arc.
Light freely through the mesh on the surface of solid zinc disc.
STOLETOV found that if a zinc side of capacitor is connected to the negative pole of the voltage source (a cathode), the galvanometer connected to the circuit indicates current.If the cathode is a grid, then there is no current.So, zinc plate illuminated emits negatively charged particles, which are responsible for the current existence between her and the net.
STOLETOV studying the photoelectric effect, the physics of which has not yet opened, took for his experiments wheels of the different metals: aluminum, copper, zinc, silver, nickel.Attach them to the negative terminal of the voltage source, he watched under the arc in his circuit pilot plant an electric current.This current is called the photocurrent.
By increasing the voltage between the capacitor plates, the photocurrent increased, reaching a certain voltage to its maximum value called the saturation photocurrent.
Exploring the photoelectric effect, the physics of which is inextricably linked to the dependence of the photocurrent saturation of luminous flux incident on the cathode plate, Stoletov established the following law: the photocurrent saturation, will be directly proportional to the incident light flux plaque.
This law is called Stoletov.
Later it was found that the photocurrent - the flow of electrons, light torn metal.
theory of the photoelectric effect has found wide practical application.Since devices have been created, which are based on this phenomenon.They are called solar cells.
photosensitive layer - cathode - covers almost the entire inner surface of a glass cylinder, except for a small window to access the light.The anode is a wire ring, reinforced inside the container.The container - a vacuum.
If you connect the ring to the positive pole of the battery and the light-sensitive layer of metal through the galvanometer with its negative pole, then the light layer proper light source in the chain will be current.
You can turn off the battery at all, but then we will see the current, only a very weak, since only a tiny part of the light ejected electrons will fall on the wire ring - the anode.To enhance the effect of the order is necessary to stress 80-100.
photoelectric effect, the physics of which is used in such cells can be observed using any metal.However, most of them, such as copper, iron, platinum, tungsten, only sensitive to ultraviolet rays.Mere alkaline metals - potassium, sodium and cesium, especially - are sensitive to visible light.They also are used for the manufacture of solar cells cathodes.
