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ISC Class XII Prelims 2023 : Physics

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INSTITUTE OF ACADEMIC EXCELLENCE AND MUSIC 421 BD, SALTLAKE CITY, KOLKATA, NEAR BD MARKET Mobile: 9874555320/9874022085 Academic year 2022-2023 Subject PHYSICS Class 12 Topics: Wave optics, current electricity Maximum Marks 30 Section A (10 marks) Time 60 min [10 1=10] 1. Two waves having the intensities in the ratio of 9 : 1 produce interference. The ratio of maximum to minimum intensity is (a) 10 : 8 (b) 9 : 1 (c) 4 : 1 (d) 2 : 1 2. In a Young s double slit experiment, the source is white light. One of the holes is covered by a red filter and another by a blue filter. In this case (a) there shall be alternate interference patterns of red and blue. (b) there shall be an interference pattern for red distinct from that for blue. (c) there shall be no interference fringes. (d) there shall be an interference pattern for red mixing with one for blue. 3. In Young s double-slit experiment, the distance between the slit sources and the screen is 1 m. If the distance between the slits is 2 mm and the wavelength of light used is 600 nm, the fringe width is (a) 3 mm (b) 0.3 mm (c) 6 mm (d) 0.6 mm 4. A potentiometer is an accurate and versatile device to make electrical measurement of EMF because the method involves (a) potential gradients (b) a condition of no current flow through the galvanometer (c) a combination of cells, galvanometer and resistance (d) cells 5. Which of the following characteristics of electrons determines the current in a conductor? (a) Drift velocity alone (b) Thermal velocity alone (c) Both drift velocity and thermal velocity (d) Neither drift nor thermal velocity 6. Why are coherent sources required to create interference of light? 7. What will be the effect on interference fringes if red light is replaced by blue light? 8. No interference pattern is detected when two coherent sources are infinitely close to each other. Why? 9. The emf of a cell is always greater than its terminal voltage. Why? Give reason. 10. Define the term Mobility of charge carries in a conductor. Write its SI unit. Page 1 of 3 Section B (5 marks) [5 1=5] 11. Diffraction of Light The phenomenon of bending of light around the sharp corners and the spreading of light within the geometrical shadow of the opaque obstacles is called diffraction of light. The light thus deviates from its linear path. The deviation becomes much more pronounced, when the dimensions of the aperture or the obstacle are comparable to the wavelength of light. (i) Light seems to propagate in rectilinear path because (a) (b) (c) (d) its spread is very large its wavelength is very small reflected from the upper surface of atmosphere it is not absorbed by atmosphere (ii) In diffraction from a single slit the angular width of the central maxima does not depend on (a) (b) (c) (d) l of light used width of slit distance of slits from the screen ratio of l and slit width (iii) For a diffraction from a single slit, the intensity of the central point is (a) (b) (c) (d) infinite finite and same magnitude as the surrounding maxima finite but much larger than the surrounding maxima finite and substantially smaller than the surrounding maxima (iv) Resolving power of telescope increases when (a) (b) (c) (d) wavelength of light decreases wavelength of light increases focal length of eye-piece increases focal length of eye-piece decreases (v) In a single diffraction pattern observed on a screen placed at D meter distance from the slit of width d meter, the ratio of the width of the central maxima to the width of other secondary maxima is (a) (b) (c) (d) 2:1 1:2 1:1 3:1 Page 2 of 3 Section C (10 marks) 12. Plot a graph showing variation of voltage Vs the current drawn from the cell. How can one get information from this plot about the emf of the cell and its internal resistance? [2] 13. Use Kirchhoff s laws to determine the value of current I1 in the given electrical circuit [2] 14. Draw the intensity distribution for (i) the fringes produced in interference, and (ii) the diffraction bands produced due to single slit. Write two points of difference between the phenomena of interference and diffraction. [3] 15. The intensity at the central maxima (O) in a Young s double slit experiment is I0. If the distance OP equals one-third of the fringe width of the pattern, show that the intensity at point P would be. [3] Section D (5 marks) 16. Use Huygens principle to show how a plane wavefront propagates from a denser to rarer medium. Hence, verify Snell s law of refraction. [5] _______________________________________________________________________________________________ Page 3 of 3

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Additional Info : ISC Class XII Prelims 2023 : Physics Wave Optics & Electricity
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