CBSE Board Physics Question Paper, 1997
Q. 16. Draw a graph showing the variation of stopping potential with frequency of modes: radiations in relation to photoelectric effect. Deduce an expression for the slope of this graph u>. Einstein’s photoelectric equation.
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Q. 17. Define disintegration constant and mean life of a radioactive substance. Give units for each.
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Q. 18. Distinguish between N-type and P-type semiconductor on the basis of energy-band diagram.
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Q. 19. State Gauss’s theorem. Using Gauss’s theorem, derive an expression for electric field intensity at any point inside a hollow charged conducting sphere.
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Q. 20. Why is potentiometer preferred to a voltmeter for measuring e.m.f. of a cell ?
The potentiometer wire AB shown in the figure is 400 cm long. When should the free end of galvanometer be connected on AB so that the galvanometer shows no deflection ?
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Q. 21. A potential difference V is applied across a conductor of length L and diameter D. How are the electric field E and resistance of the conductor affected when in turn
(i) V is halved (ii) L is halved and
(iii) D is doubled ? Justify your answer in each case.
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Q. 22. When an alternating voltage of 220 V is applied across a device X, a current of 0.5 A flows through the circuit and is in phase with applied voltage. When same voltage is applied across another device Y, the same, current again flows through the circuit but it leads the applied voltage by Jill radian.
(a) Name the device X and Y.
(b) Calculate the current flowing in the circuit when same voltage is applied across the series combination of X and Y.
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Q. 23. Derive an expression for the fringe width in Young’s double slit interference experiment.
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Q. 24. What is Doppler effect in light ? The spectral lines for a given element in light received from a distance star is shifted towards longer wavelength by 0.025% ? Calculate the velocity of the star in the line of sight.
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Q. 25. Draw a labelled ray diagram for a refracting type astronomical telescope. How will its magnifying power be affected as increasing (i) the focal length ; and (ii) the aperture of eye piece ? Justify your answer.
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Q. 26. Establish the relationship between object distance, image distance and radius of curvature for a convex mirror.
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Q. 27. Define solar constant. Derive an expression for the surface temperature of the sun in terms of solar constant and solar radius.
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Q. 28. Explain with the help of a labelled diagram, the underlying principle, construction and working of a moving coil galvanometer,
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Q. 29. State Bohr’s postulates. Using these postulates during an expression for the total
energy of an electron in the orbit of an atom. What does negative value of the energy signify ?
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Q. 30. Explain with the help of a labelled circuit diagram, the use of NPN transistor as an amplifier in common emitter configuration. Why is common emitter amplifier preferred over the common base amplifier ?
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