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

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Presentation on theme: "The photoelectric effect is best explained by treating light as a Particle."— Presentation transcript:

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

6 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!!

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

8 METAL PHOTONS e e e e ELECTRONS e

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

10 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

11 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:

12 frequency y intercept Slope h FoFo

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

14 frequency y intercept Slope h FoFo

15 Mathematical Model: K max = hf -

16 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

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

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

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21 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?

22 The maximum speed is: 3.0x10 5 m/s

23 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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