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CBSE CLASS XII

Physics

1. Name the device which works under the principle of velocity selector?
2. Define  1 Ampere the unit of a.c current and how does it vary from d.c current?
3. Is the magnitude of displacement current less, equal or greater than the conduction current?explain
4. a)Why secondary rainbow is fainter than the primary rainbow? b) why clouds are appearing white?
5. In a wave picture of light, the intensity of light is determined by square of amplitude of wav e. What determines the intensity of light in photon picture of light?
6. The  maximum K.E of emitted photo electron is 15eV. Find its stopping potential.
7. Draw a graph to show the variation of impact parameter (in alpha particle scattering)with scattering angle Ѳ.
8. Name a communication channel which can offer a transmission bandwidth in excess of 100 GHZ.
9. If accelerating voltage of anode is doubled what will be the change in De Broglie’s wave length of electron?
10. Waves from which portion of EM spectrum are utilized to identify defects in crystals. Write the frequency range corresponding to this zone
11. Why does the electric field inside a dielectric decrease when it is placed in an external electric field?
12. Draw the symbol and write truth table of NOR gate.?
13. A wire is stretched to double its length. What will be the effect on  its resistivity ?
14. Two thin lenses of power +7D and -3D are in contact. What is the focal length of the combination ?
15. The radii of curvature of the faces of a double convex lens are 10 cm and 15 cm. If focal length is 12 cm, what is the refractive index of glass ?
16. What is the distance of closest approach when a 5.0 MeV proton approaches a gold nucleus?
17. It is observed that only 6.25% of a given radioactive sample is left undecayed after a period of 16 days. What is the decay constant of this sample, in day-1 ?
18. For a transistor connected in common emitter mode, the voltage drop across the collector is 2 V and β is 50. Find the base current, if RC is 2 K
19. State the reason , why GaAs is most commonly used in making of a solar cell.
20. A square wave is applied to p-n junction diode as shown in the figure. Draw the output waveform.

Submitted By : Mr. Raghu Sharma
Email: [email protected]