Q. 17. The spectral line emitted by a star, known to have a wavelength 6,500 A, when observed in the laboratory appears to have a wavelength of 6,525 A. What is the speed of the star in the line of sight relating to the earth ? Is the star approaching or receding ? 2
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Q. 18. Draw a labelled diagram to show image formation in a compound microscope.
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Q. 19. Sketch the energy level diagram for hydrogen atom. Mark the transitions corresponding to Lyman and Balmer series. 2
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Q. 20. The luminosity of a star is 10,000 times that of the sun and its surface temperature is 3,000 K. Assuming the surface temperature of the sun to be 6,000 K, compare the radius of the star with that of the sun. 2
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Q. 21. A ray of light while travelling from the denser to the rarer medium undergoes total internal reflection. Derive the expression for the critical angle in terms of the speed of light in two media.
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Q. 22. Name the logic gate shown below and write down the truth table.
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Q. 23. State Faraday’s laws of electrolysis. Derive the relation connecting chemical equivalent and electrochemical of an element. 3
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Q. 24. A proton and an alpha particle having the same kinetic energy are in turn allowed to pass through a uniform magnetic field perpendicular to their direction of motion. Compare the
radii of the paths of proton and a-particle. [Masses of proton and a are 1.67 X 10-27 kg and 6.6 x 10-27 kg respectively.]
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Q. 25. With the help of a circuit diagram explain how the internal resistance of a cell can be determined using a potentiometer. Write the formula used.
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Q. 26. Explain the principle and working of a tangent galvanometer with the help of a diagram.
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Q. 27. The radius of curvature of each face of a biconcave lens, made of glass of reflective index 1.5 is 30 cm. Calculate the focal length of the lens in air. 3
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Q. 28. Explain Rutherford’s experiment on alpha particles and state the significance of the results.
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Q. 29. What are cathode rays ? How are they produced ? State two properties of these rays. 3
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Q. 30. Explain with the help of a labelled circuit diagram, the use of a transistor as an oscillator.
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Q. 31. State Gauss’s theorem in electrostatics. Using it, derive an expression for electric field at any point due to an infinite plane sheet of charge of uniform charge density a, 5
Define capacitance of a capacitor. Give its SI units. For a parallel plate capacitor, prove that the total energy stored in a capacitor is ½ CV2 and hence derive the expression tor the energy densityof the capacitor.
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Q. 32. Distinguish between terms reactance and impedance of AC circuit. Prove that an ideal capacitor connected to AC does not dissipate power.
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