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Published byAva Morales Modified over 2 years ago

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The photoelectric effect is best explained by treating light as a Particle

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Albert Einstein explained the photo- electric effect in He won the Nobel Prize for his work in He also published his special theory of relativity in the same year. I was only 26 in 1905!!

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The Photoelectric effect occurs when light is shown on a metal. The light ejects electrons from the metal producing an electric current..

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METAL PHOTONS e e e e ELECTRONS e

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According to classical physics, high intensity light would eject electrons with greater kinetic energy. Experimental results contradicted this theory.

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Experiments showed that the kinetic energy of the electrons depended on the frequency of the light. Low frequency light, no matter how intense could not eject a single electron. High frequency light with a very small intensity was able to eject electrons with a large kinetic energy

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Experiments were done to find the relationship between the kinetic energy of the ejected electrons and the frequency of the incident light. They resulted in the following graph:

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frequency y intercept Slope h FoFo

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Written Relationship:: The kinetic energy of the ejected electron is proportional to the frequency of the incident light.

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frequency y intercept Slope h FoFo

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Mathematical Model: K max = hf -

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Light is a particle, called a photon. Each particle has a energy that is directly proportional to the frequency of the light. E = hf E = Energy h = Plancks Constant (6.63x Js) f = frequency of the light

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represents the work function of the metal. It is the minimum energy needed to eject an electron from the metal.

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PRACTICAL APPLICATIONS The Photoelectric Cell video cameras electric eyes burglar alarms night lights solar power video games

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Example: The work function for a particular metal is 3.2x J. If the metal is illuminated with light of wavelength 550nm. What is the maximum speed of the emitted electrons?

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The maximum speed is: 3.0x10 5 m/s

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Sample Quiz The photoelectric effect is best explained by treating light as a ___________? Who won the Nobel Prize for the explaining the photoelectric effect? List two practical applications of the photo electric effect.

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