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When electromagnetic radiation such as light hits a material like a zinc plate, it leads to the emission of electrons and produces a photoelectric effect. This electromagnetic effect was finally explained by the famous scientist Einstein. However, before him, many other physicists like Heinrich Rudolf Hertz and Lenard observed it and presented it in their way. However, before them, Maxwell explained the electromagnetic field in his publication “A dynamical theory of the Electromagnetic Field” in 1865. He stated that both the electric field and magnetic field travel through space in the form of waves moving at the speed of light.
Observations of the Photoelectric Effect
Heinrich Rudolf Hertz was a German physicist. He is known for discovering the photoelectric effect, which was introduced in 1887. Hertz was experimenting to prove the electromagnetic theory of light given by Maxwell; he noticed something strange at that time. Hertz used a gap of the spark that consisted of two sharp electrodes placed at a small distance so that the spark of electricity could be produced to detect the presence of electromagnetic waves.
He noticed it closely by placing the spark into a dark box and observed that the length of the spark reduced. Then he took out the spark from the dark box and placed it into a glass box. He noticed that the length of the spark increased. After this, he took out the spark from the glass box and placed it into a box of quartz. He noticed that the length of the spark increased further. This experiment leads to observing the effect of photoelectric for the first time.
After a year, a physicist named Wilhelm Hallwarchads confirmed these results by Hertz. He demonstrated that the light showed the ultraviolet light on a zinc plate connected to a battery-generated current due to electron emission.
In 1898 physicist J.J.Thomson observed that the amount of current varies due to the variation occurring in the frequency and intensity of the ultraviolet radiation being used.
Hertz Lenard Observations
In 1902, a physicist named Philipp Leonard explained the phenomenon and stated that the kinetic energy of electrons emitted increased with the frequency of the radiation used. Thus could not explain Maxwell’s theory which was proved correct by Hertz. According to Leonard, the kinetic energy of electrons should be dependent only on the intensity of light rather than the frequency of light.
A few years later, a famous scientist, Einstein, brought the resolution to the theory by explaining the photoelectric effect of light.
Electromagnetic Waves
Electromagnetic waves are also known as electromagnetic radiation. They are composed of oscillating magnetic and electric fields. The electromagnetic wave may be defined as the variation between an electric field and a magnetic field. As the name “electromagnetic” suggests, these waves are formed when an electric field and magnetic field come in contact. The electric field and magnetic field of an electromagnetic wave are connected at the right angles, which means they are perpendicular. Not only this, the electric wave and the magnetic wave are perpendicular to the direction of the electromagnetic wave.
Characteristics of Electromagnetic Waves
- The velocity of the electromagnetic wave is always constant, which is 3.00 × 108 m/s in a vacuum
- Both electric and magnetic fields do not deflect them; however, they show interference and diffraction
- An electromagnetic wave can travel in a vacuum, air, or solid materials
- It does not need any medium for propagating
- Whereas mechanical waves such as sound waves and water waves always need a medium to travel through
- Electromagnetic waves are transverse, which means they are measured by their amplitude or height and wavelength
- The wavelength is the difference between the highest and lowest points of two consecutive waves
- The highest point of electromagnetic waves is the “crest”, and the lowest is the “trough”
- The electromagnetic waves have a spectrum which means they can be split in the range of frequencies
- They are identified as waves like microwave, radio waves, infrared waves, x-rays, gamma rays, etc
Important Topics
Conclusion
Thus we can see how the experiments conducted by different physicists like Hertz, Lanard, Maxwell, Joseph John Thompson, etc., explained the phenomenon of the photoelectric effect in their ways. However, all of these explanations were incomplete as they were confused and did not understand light’s nature. Albert Einstein gave the final demonstration. In 1905, he formulated a new corpuscular theory of light. According to this theory, each particle of light contains a fixed amount of energy that only depends on the light’s frequency and not its intensity. This phenomenon is known as the photoelectric effect of light. Here in simple words, we can understand the photoelectric effect as when the light contains more energy than a fixed point, and it can be used to produce electrical effects as the extended energy of light would be used to knock electrons loose and let them be free from a solid metal surface.
We have many important applications of the photoelectric effect of light. Photocell is the most important one. Photocells are found in solar panels; it causes electrons’ emission, which in turn produce current. Photocopies, phototransistors, light meters, photodiodes, etc., also include the photoelectric effect. The scintillator also uses the photoelectric effect and emits light by attracting radiation from either a source in the lab or a cosmic source.
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