Describe The Photoelectric Effect And The Dual Nature Of Light Pdf

describe the photoelectric effect and the dual nature of light pdf

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In this section, we will focus on the wave-like properties of light. Wave motion arises when a periodic disturbance of some kind is propagated through a medium.

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Around the turn of the twentieth century, it was observed by a number of physicists including Hertz, Thomson and Von Lenard that when light was shone onto a metal plate, electrons were emitted by the metal. This is called the photoelectric effect. The characteristics of the photoelectric effect were a surprise and a very important development in modern Physics.

Photoelectric effect

In old science fiction stories 's , one of the space travel themes was the use of solar sails for propulsion. The idea was that the photon pressure from the sun would push the sail like wind sails and move the spacecraft.

What once was science fiction is now reality as solar sails are being developed and tested for modern space travel. In Albert Einstein - proposed that light be described as quanta of energy that behave as particles.

A photon is a particle of electromagnetic radiation that has zero mass and carries a quantum of energy. For many years light had been described using only wave concepts, and scientists trained in classical physics found this wave-particle duality of light to be a difficult idea to accept.

A key concept that was explained by Einstein using light's particle nature was called the photoelectric effect.

The photoelectric effect is a phenomenon that occurs when light shined onto a metal surface causes the ejection of electrons from that metal. It was observed that only certain frequencies of light are able to cause the ejection of electrons.

If the frequency of the incident light is too low red light, for example , then no electrons were ejected even if the intensity of the light was very high or it was shone onto the surface for a long time. If the frequency of the light was higher green light, for example , then electrons were able to be ejected from the metal surface even if the intensity was very low or it was shone for only a short time. This minimum frequency needed to cause electron ejection is referred to as the threshold frequency.

Classical physics was unable to explain the photoelectric effect. If classical physics applied to this situation, the electron in the metal could eventually collect enough energy to be ejected from the surface even if the incoming light was of low frequency. Einstein used the particle theory of light to explain the photoelectric effect as shown in the figure below. Low frequency light red is unable to cause ejection of electrons from the metal surface.

At or above the threshold frequency green electrons are ejected. Even higher frequency incoming light blue causes ejection of the same number of electrons but with greater speed. If the frequency is equal to or higher than the threshold frequency, electrons will be ejected. As the frequency increases beyond the threshold, the ejected electrons simply move faster.

An increase in the intensity of incoming light that is above the threshold frequency causes the number of electrons that are ejected to increase, but they do not travel any faster. The photoelectric effect is applied in devices called photoelectric cells , which are commonly found in everyday items such as a calculator which uses the energy of light to generate electricity.

Photoelectric cells convert light energy into electrical energy which powers this calculator. Light has properties of both a wave and a particle. The photoelectric effect is produced by light striking a metal and dislodging electrons from the surface of the metal. Photoelectric Effect and the Particle Nature of Light In Albert Einstein - proposed that light be described as quanta of energy that behave as particles.

Summary Light has properties of both a wave and a particle.

Dual Nature of Light [PPT]

Just what is the true nature of light? Is it a wave or perhaps a flow of extremely small particles? These questions have long puzzled scientists. Let's travel through history as we study the matter. Around , Newton concluded that light was a group of particles corpuscular theory.


where h is the Planck's constant, ν is the frequency of the radiation or photon, c is the speed of light (e.m. wave) and λ is the wavelength. Properties of photons: i) A​.


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Around the turn of the twentieth century, it was observed by a number of physicists including Hertz, Thomson and Von Lenard that when light was shone onto a metal plate, electrons were emitted by the metal. This is called the photoelectric effect. The characteristics of the photoelectric effect were a surprise and a very important development in modern Physics.

Photoelectric effect , phenomenon in which electrically charged particles are released from or within a material when it absorbs electromagnetic radiation. The effect is often defined as the ejection of electrons from a metal plate when light falls on it. In a broader definition, the radiant energy may be infrared , visible, or ultraviolet light, X-rays , or gamma rays ; the material may be a solid, liquid, or gas; and the released particles may be ions electrically charged atoms or molecules as well as electrons.

In old science fiction stories 's , one of the space travel themes was the use of solar sails for propulsion. The idea was that the photon pressure from the sun would push the sail like wind sails and move the spacecraft.

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Winifreda T.

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The learning objectives in this section will help your students master the following standards:.

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Nowadays, most people would describe light as a wave, probably 1The person who discovered the photoelectric effect was none other A dual nature of light.

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Wave—particle duality is the concept in quantum mechanics that every particle or quantum entity may be described as either a particle or a wave.

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The research leading to an understanding of the nature of light and the emission and absorption processes has been of paramount importance.

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