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Phy.ppt

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this ppt is combined with both faradays law and photoeletric effect

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Phy.ppt

  1. 1. Photoeletric effect SUBMITTED BY N.KUMAR GANESH SUBMITTED TO
  2. 2. We know that the light has dual nature. INTRODUCTION: The Phenomena of interference & diffraction etc. can be explained on the basis of wave theory of light. Whereas the phenomena of Photoelectric Effect , compton effect can be explained on the basis of particle theory of light.
  3. 3. The ejection of electrons from a metallic surface when the light of suitable frequency is allowed to fall on the surface.
  4. 4. This suitable frequency is called Threshold Frequency and the corresponding wavelength is called threshold wavelength. Work function: The work function is the energy required to remove an electron from the highest filled level in the Fermi distribution of a solid.
  5. 5. •Incident light triggers the emission of (photo)electrons from the cathode. •Some of them travel toward the collector (anode) with an initial kinetic energy. •The applied voltage V either accelerates (if positive) or decelerates (if negative) the incoming electrons. •The intensity I of the current measured by the ammeter as a function of the applied voltage V is a measurement of the photoelectron properties, and therefore a measurement of the properties of the photoelectric effect.
  6. 6. Think about hitting a ball into outer space. If you don't hit it hard enough, it will just come back down. No matter how many times you hit it. If superman hit it, he could get it into space. Similarly, no matter how many photons strike the metal, if none of them has sufficient energy to eject an electron from a metal atom, you won't get a current. If the energy the taken up by the electron is sufficient to allow it to be released from the metal atom, you will get a current.
  7. 7. E Km W Km :- maximum kinetic energy of emitted electron W :- work function
  8. 8. V V :- potential difference Vs :- stopping potential ʋ :- frequency (constant)
  9. 9. Vs1 Vs2 Vs3 Ʋ1 Ʋ2 Ʋ3 The stopping potential depends on the frequency:-Higher frequencies generates higher energy electrons. Ʋ1 > Ʋ2 > Ʋ3
  10. 10. Photoelectric effect is directly proportional to intensity. If the frequency of the incident light is less than the threshold frequency then no electron ejected, no matter what the intensity. The maximum kinetic energy of the electrons depend on the frequency of the incident light. The electrons were emitted immediately - no time lag.
  11. 11. Km:- maximum kinetic energy E :- energy of photon’s W :- work function of metal
  12. 12. Km W E
  13. 13. Ch23:Electromagnetic Induction Wind turbine is an example of induction at work. Wind pushes the blades of the turbine, spinning a shaft attached to magnets. The magnets spin around a conductive coil, inducing an electric current in the coil, and eventually feeding the electrical grid.
  14. 14. Ch23:Electromagnetic Induction Wind turbine is an example of induction at work. Wind pushes the blades of the turbine, spinning a shaft attached to magnets. The magnets spin around a conductive coil, inducing an electric current in the coil, and eventually feeding the electrical grid.
  15. 15. Induced Emf and Induced Current (a) When there is no relative motion between the coil of wire and the bar magnet, there is no current in the coil. (b) A current is created in the coil when the magnet moves toward the coil. (c) A current also exists when the magnet moves away from the coil, but the direction of the current is opposite to that in ( b).
  16. 16. Inducing Current With a Coil in a Magnetic Field
  17. 17. Motional Emf The Emf Induced in a Moving Conductor
  18. 18. Magnetic Flux Graphical Interpretation of Magnetic Flux The magnetic flux is proportional to the number of magnetic flux lines passing through the area.
  19. 19. A General Expression for Magnetic Flux ACosBAB )(   The SI unit of magnetic flux is the weber (Wb), named after the German Physicist W.E. Weber (1804-1891). 1 Wb = 1 T.m2.
  20. 20. EXAMPLE on Magnetic Flux A rectangular coil of wire is situated in a constant magnetic field whose magnitude is 0.50 T. The coil has an area of 2.0 m2. Determine the magnetic flux for the three orientations, shown below.
  21. 21. Faraday's Law of Electromagnetic Induction Michael Faraday found experimentally that the magnitude of the induced emf is proportional to the rate at which the magnetic flux changed. Faraday’s law can be written as, .; AB t N     where N is the number of turns in the loops, A is the area of one loop, ξ is the induced emf, and B┴ is the perpendicular component of the magnetic field.
  22. 22. Lenz's Law .; AB t N     The SI unit for the induced emf is the volt, V. The minus sign in the above Faraday’s law of induction is due to the fact that the induced emf will always oppose the change. It is also known as the Lenz’s law and it is stated as follows, The current from the induced emf will produce a magnetic field, which will always oppose the original change in the magnetic flux.
  23. 23. Application of Lenz’s Law
  24. 24. An Induction Stove The water in the ferromagnetic metal pot is boiling. Yet, the water in the glass pot is not boiling, and the stove top is cool to the touch. The stove operates in this way by using electromagnetic induction.
  25. 25. An Automobile Cruise Control Device
  26. 26. A Ground Fault Interrupter
  27. 27. Electric Generator
  28. 28. Pickup coil in an electric guitar

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