No matter how the average person is far in his daily life from the once-gone school curriculum, it is no, no, and it will make you remember. This is exactly what happens when it comes to the phenomenon of an external photoelectric effect.
Definition
The photoelectric effect in physics is considered to be the process of alignment of electrons in atoms, molecules of matter, which occurs and occurs under the influence of light. And the external photoelectric effect is a process in which electrons are knocked out by light with such force that they fly out of the outer limits of their substance.
A bit of history and practice
For the first time on this amazing fact, the German physicist Heinrich Hertz drew attention in the distant 1887 year. The study of the discovery was continued by Hertz's colleague, the Russian physicist Stoletov. And the brilliant Einstein developed the theory of the photoelectric effect based on the ideas of quantum physics. Since then, the external photoelectric effect has been studied quite deeply and comprehensively, and the knowledge gained is fully applied in the development and production of devices based on photocells. If we take the most elementary example, then this is an automatic garage door that works on photocells.
Mechanisms of this type operate on electrical energy. However, solar cells that use only an external photoelectric effect do not completely transform the energy received by radiation into electrical energy. Therefore, to use them as sources of electricity does not make much sense, which can not be said about automation. It is with the help of light beams that the electrical circuits are controlled in automatic mechanisms.
Without exaggeration, it can be argued that the discovery of the photoelectric effect was a truly revolutionary event in physics. Here are its most significant consequences:
- before the scientists, the secret of the nature of light, the light ray, was revealed;
- the cinema from the silent became “talking,” methods of voice acting were invented, and the very fact of transmitting a moving image was also made possible thanks to the photoelectric effect;
- creation of such machines and “smart machines” on the basis of photoelectronic devices, which, according to the set parameters, produce various parts without human intervention;
- many different mechanisms based on the work of photoelectronic automation.
Thus, the photoelectric effect itself and its application have become a kind of breakthrough in modern technology.
Classification of photocells
Photo effects are divided into several types depending on their properties and functions.
- External photoelectric effect (in another way - photoelectron emission). Electrons that fly out of the substance when it occurs are called photoelectrons. And the electric current that they form when they orderly move along an external electric field has come to be called the photocurrent.
- Internal photoelectric effect affecting the photoconductivity of a substance. It occurs when electrons are redistributed across semiconductors and dielectrics depending on their energy state and the state of aggregation - solid or liquid. The redistribution phenomenon occurs under the influence of light. It is then that the conductivity of the substance increases, i.e. the effect of photoconductivity is obtained.
- The valve photoelectric effect is the transition of photoelectrons from their bodies to other solids (semiconductors) or liquids (electrolytes).
An external photoelectric effect underlies the operation of modern vacuum photocells. They are made in the form of glass flasks, in which the inner surface is partially covered with a thin layer of metal spraying. Insignificant layer thickness provides a small working output. The transparent window of the bulb transmits light inside, and the anode inside it in the form of a wire loop or disk captures photoelectrons. If the anode is connected to the positive pole of the battery, the circuit will close, and an electric current will flow through it. Those. vacuum photocells can turn relays on or off.
By combining photocells and relays, you can create various "seeing" machines, for example, a machine in the subway.
So, being the foundation of many production processes, the external photoelectric effect as a great physical discovery became the key to the success of industrial automation.