If anode made more negative, electrons are repelled back towards cathode as not enough KE to reach anode. When pd applied, no extra electrons generated, electrons emitted from cathode flow towards anode, therefore constant photocurrent I detected. Photoemission Experiment (Milikan’s Verification of Einstein’s Equation): Thus does not depend on time of exposure, but rather energy and frequency of light photons. Once the electron absorbs a photon of sufficient energy, it will be ejected from the surface. Thus there is a minimum threshold frequency below which no electrons will be emitted from the surface.Įxplain why observation consistent with particle theory of light: Light energy travels in packets of energy called photons.
The work function is the minimum amount of energy required to remove an electron from the surface of the metal. The energy of each photon=hf where h is the Planck constant. How does Einstein’s photoelectric theory account for threshold frequency?: The light incident on the surface consists of photons, “packets of energy”. In word: Photon energy = Work function energy + maximum KE of emitted photoelectrons Work function: Minimum work done to overcome attractive forces between the electron and the ions on the cold metal surface/ Minimum amount of energy required for an electron to escape from the surface of a cold metal. Remaining energy converted to KE of electron as it escapes. Photon does work to overcome the attractive electric forces between the electron and the ions on the metal surface. Light photons penetrate surface of metal plate and collide with electrons in metal: Intensity of the light beam is directly proportional to the number of photons passing through a unit cross-sectional area per unit time ( ). Threshold frequency: Minimum frequency of EM light required for electrons to be emitted from surface of metal.Įinstein’s explanation of Photoelectric effect: A beam of light consists of a stream of photons, and each photon has an energy E=hf.
The emission of electrons from the surface of a cold metal when electromagnetic radiation of sufficiently high frequency is shone on it. WAVE NATURE OF PARTICLES (LIGHT PHOTONS AND ELECTRONS) Photoelectric Effect:
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