Khusanova Nargiza Farkhod
By: Khusanova Nargiza Farkhod
Abstract: Experiments with light show that in some cases the wave properties of light are more pronounced, while in other cases it is necessary to consider light as a particle or quantum to explain the obtained results will come.
Key words: Light, Stoletov’s laws, electronic, external photoelectric effect
The fact that light has pressure or the phenomenon of photoelectric effect is explained by the concept of quantum (particle) of light. When light falls on a substance, it gives its energy to the substance. As a result, different effects may occur. In the most general case, the substance that absorbs light heats up, its temperature rises.
But often, part of the light turns into heat, and the rest turns into other types of energy. Converging lenses are used to experimentally observe the thermal effects of radiation. For example, by focusing the sun’s rays on a flammable substance through a lens, it is possible to burn or burn this substance. With powerful laser beams, very fine holes can be made in very hard materials such as diamond.
So, under the influence of light energy, it is possible to melt and vaporize hard-to-dissolve materials. It is a well-known phenomenon that the warming of the earth’s surface occurs due to the heat of the sun’s rays. The amount of energy reaching the Earth through radiation is greater than the energy used in all industries on Earth.
According to calculations www.z 9 6, an average of 1370 J of energy per second per square meter of cross section of the Earth’s surface. This quantity is called Solar constant. The phenomenon of electrons escaping from substances under the influence of light is called the external photoelectric effect. Electrons flying out of matter are called photoelectrons.
The discovery of the photoelectric effect, or photoeffect for short, can be dated to 1887, because in that year Gers observed that a spark was facilitated when a gap between energized electrodes was illuminated with ultraviolet rays. Later Galvaks, A.G. Systematic experiments of Stoletov and a number of other researchers proved (1888) that charged particles are released from Herz electrodes under the influence of light and ionize gas molecules, causing a spark. A.G. Stoletov was the first to apply a small voltage between the electrodes in his experiments on the photoeffect, and the result he thought turned out to be better than expected.
Ultraviolet rays coming out of the strong discharge nozzle pass through the mesh and fall on the zinc plate and knock out charged particles from it. These particles fall into a grid connected to a chain. A photocurrent flows through the galvanometer. So, under the influence of light, negatively charged particles are released. When ultraviolet rays fall on the head of a negatively charged electroscope, it is possible to observe that the leaves of the electroscope close quickly, that is, the electroscope quickly discharges.
An uncharged plate becomes positively charged when exposed to light. Therefore, it became necessary to check the charge and direction of the particles released under the influence of light. By 1898, Leonard and Òomson determined εm based on the deflection of the emitted particles in an electric and magnetic field. It was proved that the determined quantity corresponds to a particle called an electron. Based on the conducted experiments, A.G. Stoletov created the following laws for the photoeffect:
- The number of photoelectrons released from the substance is linearly dependent on the illumination of the substance or the light flux falling on it, i.e.: NÔ~ E or NÔ~ Ô. Therefore, the light is directly proportional to the light flux falling on the substance.
- The energy of the photoelectrons flying out of the substance is directly proportional to the frequency of the light falling on the substance from the outside, i.e.: E0~v, v— light frequency of
- The number of photoelectrons released from the substance does not depend on the frequency of light falling on the substance from outside.
- The energy of the electrons flying out of the substance does not depend on the light flux. The following experiment is used to study the laws of photoeffect (external photoeffect). Cathode (photocathode) and anode electrodes are installed in a glass cylinder with air sucked in.
Light is directed to the photocathode through a glass quartz window specially installed on the side of the glass cylinder. A negative voltage is applied to the cathode, and a positive voltage is applied to the anode. A sensitive galvanometer photocurrent in the anode circuit. K measures A. If the power source is not connected to the circuit, the electrons leaving the cathode will be very highThe z part reaches the anode and the galvanometer shows a small current. When the switch is connected, even low-energy electrons can reach the anode under the influence of the field. 9 8 The current passing through the galvanometer is called the saturation current.
If we change the direction of the applied field between the cathode and the anode (reverse the source poles) and increase the field, the photocurrent value decreases to zero. This connection is shown in Figure 78.
If the location and shape of the electrodes change and the space between the electrodes is broken, the photocurrent characteristic changes. The best shape for the electrodes is a spherical capacitor. The cathode is a small ball in the center of the sphere, and the anode is the outer electrode sphere. The saturation current I0 depends on the cathode surface, material and purity, and temperature.
If we increase the intensity of the light falling on the substance, it can be observed that the value of the saturation current increases and the photocurrent characteristic (volt-ampere characteristic – VAX) shifts slightly to the right relative to the coordinate axis. This law was tested by varying the light intensity over a wide area. The obtained results are well reproducible. If we look at figure 78, if the reverse voltage is applied to the anode, the value of the photocurrent will be zero at a certain voltage – U0. This can be concluded.
The electric field repels the photoelectrons coming out of the cathode at a high speed and prevents them from falling to the anode. If we increase the frequency of light falling on the surface of the photocathode, the value of the voltage at which the photocurrent tends to zero increases again.
In other words, the initially given burning potential is the burning potential – U0, as it cannot hold the electrons coming out of the cathode. U I I 0 –U However, all the electrons flying from the cathode under the influence of light cannot reach the anode.
If we increase the area between the cathode and the anode, all the electrons will reach the anode. In this case, the current in the galvanometer increases sharply and then remains unchanged. Even when the electrodes are placed in the most convenient way, the value of the photocurrent does not drop to zero suddenly, but gradually decreases to zero. So, it can be said that the energy of electrons is different.
If the electrons with a small speed are caught in a smaller closing potential, it is necessary to give a larger closing potential to stop the electrons with a high speed. From these conclusions it follows that the formula has an important physical significance.
First of all, the speed to be determined is the speed that electrons acquire under the influence of light. Secondly, the energy of the electrons flying out of the substance cannot be quantitatively equal to the energy of light.
Because, for example, when light falls on a metal surface, it transfers its energy to free electrons in the crystal, and the electrons, in turn, lose a certain amount of energy to leave the surface. The lost energy is spent on the work of removing electrons from the metal.
Review questions
- What do you understand by the thermal effect of light?
- Explain Stoletov’s experiments.
- Describe Stoletov’s laws.
- What is the external photo effect?
- Explain the photocurrent volt-ampere characteristic.
- What do the maximum kinetic energy and output work of photoelectrons depend on?
Khusanova Nargiza, Farkhod qizi, was born on November 30, 2003 in Khatirchi district of Navoi region. He graduated from general secondary school No. 78 in Khatirchi district, Navoi region. Currently, he is a student of the 2nd stage of the Bukhara State Pedagogical Institute. Student of the Year -23 OTM winner.
He is the author of a monograph on the topic of determining the constant current power bridge in 2024, and is currently working as a coordinator of the “Mushoira Club” at the institute. Bukhara State Pedagogical Institute student coordinator of the primary organization Youth Union. Girls’ Voice Bukhara city sports and health department coordinator. Institute’s Young Politician Girls Club coordinator. And also active member of UzliDep in Bukhara
References and websites
- www.ziyouz.com library
- Physics. Book 3. The text of the lectures (A. Nomonkhojayev, M. Fattohov, etc.)
Similar Posts by The Mt Kenya Times:
- Mt Kenya Times ePAPER August 27, 2026
- Opposition will have a candidate by April, says Gachagua
- Kalonzo takes his campaign to the people across three counties
- Kenya’s election technology tender: A KSh10B procurement under fire
- The goon question: What Ruto’s vow to act personally really means for Kenya
About the Author
