Sample Paper – 2008
Class – Physics
Class – XII
Dual nature of matter
Q.1. State the dependence of work function on kinetic energy of electrons emitted in a photocell. If the intensity of incident radiation is doubled, what changes occur in the stopping potential and photoelectric current?
Q.2. How does the maximum kinetic energy of the emitted electrons vary with the work function?
Q.3. the frequency of incident radiation is greater than the threshold frequency in a photocell. How will the stopping potential vary if frequency is increased, keeping other factors constant.
Q.4. Why are De-Broglie waves associated with a moving football not visible. The wavelength of a photon and De-Broglie wavelength of an electron have the same value. Show that the energy of the photon is ( 2mcλ ) / h times the kinetic energy of the electron.
Q.5. Electrons are emitted from a photosensitive surface when it is illuminated by green light but electron emission does not take place by yellow light. Will the electrons be emitted when the surface is illuminated by (i) red light, and (ii) blue light?
Q.6. Ultraviolet light of wavelength 2271 A from a 100 W mercury source radiates a photo cell made of molybdenum metal. If the stopping potential is 1.3 V, estimate the work function of the metal. How would the photo cell respond to high intensity (105 Wm-2) red light of wavelength 6328 A produced by a He - Ne laser?
Q.7. Plot a graph showing the variation of photoelectric current with anode potential for two light beams of same wavelength but different intensity.
Q.8. Which experiment proved the existence of De’Broglie waves?
Q.9. Two metals “X” and “Y” have work functions 2ev and 5ev respectively. Which metal will emit electrons when irradiated with light of wavelength 400nm? Find threshold wavelength for both the metals.
Q.10. Light from the bulb falls on a wooden table but no electrons are emitted. Why?
Q.11. A 100W bulb emits yellow light of...
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