Dual Nature of Radiation and Matter Three Marks Questions

12th Standard EM

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Physics

Time : 01:00:00 Hrs
Total Marks : 45
    15 x 3 = 45
  1. What do you mean by electron emission? Explain briefly various methods of electron emission.

  2. Briefly discuss the observations of Hertz. Hallwachs and Lenard.

  3. Explain the effect of potential difference on photoelectric current.

  4. Explain how frequency of incident light varies with stopping potential.

  5. List out 'the laws of photoelectric effect.

  6. Explain why photoelectric effect cannot be explained on the basis of wave nature of light

  7. Explain the quantum concept of light.

  8. Obtain Einstein's photoelectric equation with necessary explanation.

  9. Give the construction and working of photo emissive cell.

  10. Derive an expression for de Broglie wavelength of electrons.

  11. Describe briefly Davisson Germer experiment which demonstrated the wave nature of electrons.

  12. For the photoelectric emission from cesium, show that wave theory predicts that
    i) maximum kinetic energy of the photoelectrons (Kmax) depends on the intensity I of the incident light.
    ii) Kmax does not depend on the frequency of the incident light and
    iii) the time interval between the incidence of light and the ejection of photoelectrons is very long.
    (Given: The work function for cesium is 2.14 eV and the power absorbed per unit area is 1.60 x 10-6 Wm-2 which produces a measurable photocurrent in cesium.)

  13. When light of wavelength 2200 Å falls on Cu, photo electrons are emitted from it. Find (i) the threshold wavelength and (ii) the stopping potential. Given: the work function for Cu is ϕ0 = 4.65 eV.

  14. The work function of potassium is 2.30 eV. UV light of wavelength 3000 Å and intensity 2 Wm-2 is incident on the potassium surface. i) Determine the maximum kinetic energy of the photo electrons ii) If 40% of incident photons produce photo electrons, how many electrons are emitted per second if the area of the potassium surface is 2 cm2?

  15. Light of wavelength 390 nm is directed at a metal electrode. To find the energy of electrons ejected, an opposing potential difference is established between it and another electrode. The current of photoelectrons from one to the other is stopped completely when the potential difference is 1.10 V. Determine i) the work function of the metal and ii) the maximum wavelength of light that can eject electrons from this metal

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