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Optics Model Question Paper

12th Standard

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Physics

Time : 01:00:00 Hrs
Total Marks : 40
    5 x 1 = 5
  1. If the velocity and wavelength of light in air is Va and λa and that in water is Vw and λw, then the refractive index of water is______.

    (a)

    \(\frac{V_W}{V_a}\)

    (b)

    \(\frac{V_a}{V_W}\)

    (c)

    \(\frac{\lambda_W}{\lambda_a}\)

    (d)

    \(\frac{{V_a}\lambda_a}{{V_W}\lambda_W}\)

  2. Stars twinkle due to, ______.

    (a)

    reflection

    (b)

    total internal reflection

    (c)

    refraction

    (d)

    polarisation

  3. A ray of light travelling in a transparent medium of refractive index n falls, on a surface separating the medium from air at an angle of incidents of 45o . The ray can undergo total internal reflection for the following n, ______.

    (a)

    n = 1.25

    (b)

    n = 1.33

    (c)

    n = 1.4

    (d)

    n = 1.5

  4. A man of length h requires a mirror of length at least equal to, to see his own complete image is _______________.

    (a)

    \(\cfrac { h }{ 4 } \)

    (b)

    \(\cfrac { h }{ 2 } \)

    (c)

    \(\cfrac { h }{ 2 } \)

    (d)

    h

  5. A man runs towards a mirror at a speed 15m/s. The speed of the image relative to the man is _______________.

    (a)

    15 ms-1

    (b)

    30 ms-1

    (c)

    35 ms-1

    (d)

    20 ms-1

  6. 5 x 2 = 10
  7. Obtain the equation for apparent depth.

  8. Why do stars twinkle?

  9. What are the sign conventions followed for lenses?

  10. Define focal length.

  11. Write the two conditions for total internal reflection.

  12. 5 x 3 = 15
  13. Derive the equation for angle of deviation produced by a prism and thus obtain the equation for refractive index of material of the prism.

  14. What is dispersion? Obtain the equation for dispersive power of a medium.

  15. Discuss the experiment to determine the wavelength of monochromatic light using diffraction grating.

  16. Write the drawbacks of Nicol prism.

  17. What is thin lens?

  18. 2 x 5 = 10
  19. If the distance D between an object and screen is greater than 4 times the focal length f of a convex lens, then there are two positions for which the lens forms an enlarged image and a diminished image respectively. This method is called conjugate foci method. If d is the distance between the two positions of the lens, obtain the equation for focal length of the convex lens.

  20. A beam of light of wavelength 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. What is the distance between the first dark fringes on either side of the central bright fringe?

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