![photon cut off wavelength photon cut off wavelength](https://aip.scitation.org/action/showOpenGraphArticleImage?doi=10.1063/1.2942401&id=images/medium/1.2942401.figures.f12.gif)
Thus the quantum numbers of two levels involved in the emission of photon of energy 2.55 eV are 4 and 2. The energy of the emitted photon is 2.55 eV. (b) These photons (whose energy is 2.55 eV) are by hydrogen atoms. Where hν is the energy of photons causing the photo-electric emission and W is the work-function of the emitting surface. (a) According to Einstein’s photo-electric equation, the maximum kinetic energy E K of the emitted electrons is given by (Ionization potential of hydrogen is 13.6 volt and the mass of the hydrogen atom is 1.67 x 10 -27 Kg, 1 eV = 1.6 x 10 -19 J). (d) the recoil speed of the emitting atom assuming it to be at rest before the transition. (c) the change in the angular momentum of the hydrogen atom in the above transition, and (b) the quantum numbers of the two levels involved in the emission of these photons. (a) the energy of the photons causing photoelectric emission. The kinetic energy of the fastest photo-electrons emitted from sodium is 0.73 eV. a, b, c – different intensites.Įxample : Light from a discharge tube containing hydrogen atoms falls on the surface of a piece of sodium. The stopping potential Vs depends only on the metal and does not depend on the intensity of incident light. This potential is known as the stopping potential and depends only on the material of the photocathode and the frequency of light. It is observed that when the applied retarding potential is increased, the photocurrent eventually becomes zero. This is because the electrons are retarded, and most of the elecrons are unable to reach the opposite electrode. If the polarity of the battery is reversed and the applied potential is gradually increased, the photo-current starts decreasing. When the potential difference across the tube is increased, the Photo current increases and finally reaches a maximum value (Is) which depends on the intensity of light. With an increase in potential difference across the tube, the number of electrons reaching the anode increases. The experimental arrangement for observing the photoelectric effect is shown in the following figure.Īll the ejected electrons are not able to leave the surface and hence are not able to reach the anode.
![photon cut off wavelength photon cut off wavelength](http://i1.ytimg.com/vi/IOav69n1FVU/maxresdefault.jpg)
(ii) The number of Photo electrons ejected per unit time depends on the intensity of the light, frequency of light being kept constant (i) The kinetic energy of the ejected electron depends linearly on the frequency of the photon. If the frequency of the photon is ν and threshold frequency for the metal is ν o, then that the photoelectron can have is given by the expression Suppose that, the energy of an incident photon is E and the work function of the metal is W. The maximum K.E.
![photon cut off wavelength photon cut off wavelength](http://hyperphysics.phy-astr.gsu.edu/hbase/imgmod/pelec4.png)
In practice, the emitted photo electrons have a range of kinetic energies. Work Function W = h ν o Where, ν o is Threshold FrequencyĮlectrons are, therefore, emitted only if the frequency of the photon is greater than the threshold frequency. Work function is different for different metals.Ī photon having an energy at least equal to the work function can eject electron from the metal, frequency of such a photon whose energy is just equal to the work function is called Threshold Frequency. The minimum energy needed to eject an electron from a metal is known as the work function of the metal.