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photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
photo electric effect slides
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photo electric effect slides

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  1. Izhar Ullah (Reg#CSEE-XF12-200)
  2. OUTLINE: Introduction.  Laws of Photo Electric Effect.   EINSTEIN’S EQUATION.  APPLICATION.
  3. INTRODUCTION: First observed by Heinrich Hertz in 1887, the phenomenon is also known as the Hertz effect.  Hertz observed and then showed that electrodes illuminated with ultraviolet light create electric sparks more easily. 
  4. The ejection of electrons from a metallic surface when the light of suitable frequency is allowed to fall on the surface.
  5. • 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.
  6. • 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.
  7. EINSTEIN’S EQUATIONS FOR THE PHOTOELECTRIC EFFECT Einstein's interpretation of the photoelectric effect results in equations which are valid for visible and ultraviolet light: energy of photon = energy needed to remove an electron + kinetic energy of the emitted electron  hν = W + E Where  h is Planck's constant ν is the frequency of the incident photon W is the work function, which is the minimum energy required to remove an electron from the surface of a given metal: hν0 E is the maximum kinetic energy of ejected electrons: 1/2 mv2 ν0 is the threshold frequency for the photoelectric effect m is the rest mass of the ejected electron v is the speed of the ejected electron
  8. EINSTEIN’S EQUATIONS FOR THE PHOTOELECTRIC EFFECT :  No electron will be emitted if the incident photon's energy is less than the work function.
  9. Km:- maximum kinetic energy E :- energy of photon’s W :- work function of metal
  10. WORK FUNCTIONS OF SELECTED METALS Metal Ø (eV) Na 2.46 Al 4.08 Cu 4.70 Zn 4.31 Ag 4.73 Pt 6.35 Pb 4.14 Fe 4.50
  11. APPLICATION OF PHOTO ELECTRIC EFFECT:  Television Camera Tubes  Light-Activated Counters  Automatic Doors  Intrusion Alarms  Turn on Street Lights at Dawn

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