Light Important Questions

8th Standard

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Science

Time : 01:00:00 Hrs
Total Marks : 50
    6 x 1 = 6
  1. Which of the following has curved reflecting surface?

    (a)

    plane mirrors

    (b)

    spherical mirrors

    (c)

    simple mirrors

    (d)

    None of the above

  2. The centre of a sphere of which the reflecting surface of a spherical mirror is a part is called

    (a)

    pole

    (b)

    centre of curvature

    (c)

    cradius of curvature

    (d)

    aperture

  3. The distance from the pole to the focus is called

    (a)

    Pole length

    (b)

    focal length

    (c)

    principal axis

    (d)

    None of the above

  4. If the focal length of a spherical mirror is 10 cm, what is the value of its radius of curvature?

    (a)

    10 cm

    (b)

    5 cm

    (c)

    20 cm

    (d)

    15 cm

  5. The refractive index of water is

    (a)

    1.0

    (b)

    1.33

    (c)

    1.44

    (d)

    1.52

  6. In which mirror the following statement is labeled?

    (a)

    Convex mirror

    (b)

    Concave mirror

    (c)

    Plane mirror

    (d)

    Spherical mirror

  7. 4 x 1 = 4
  8. Nature of the images formed by a convex mirror is _________.

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    virtual image

  9. It the angle of incidence is 45°, then the angle of reflection is ______.

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    45°

  10. If an object is placed between two mirrors which are parallel to each other, the number of images formed is _________

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    Infinite

  11. __________ is the best reflector of light

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    Silver

  12. 5 x 1 = 5
  13. Convex mirror

  14. (1)

    sin i /sin r = μ

  15. Regular reflection

  16. (2)

    Rear - view mirror

  17. Snell’s law

  18. (3)

    Kaleidoscope

  19. Refractive index

  20. (4)

    plane mirror

  21. Refraction

  22. (5)

    Bending of light

    1 x 2 = 2
  23. Assertion (A): The pencil appears, to be bent when we see it through the glass of water.
    Reason (R): Lightray travels from a denser medium to a rarer medium, it has deviated from its straight-line path.
    a) If both assertion and reason are true and reason is the correct explanation of the assertion.
    b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
    c) Assertion is true but the reason is false.
    d) Assertion is false, but the reason is true.

  24. 3 x 2 = 6
  25. Curved mirrors produce images that are either enlarged or diminished.

  26. In dispersion, the violet-colored light has a' long wavelength and is deviated more.

  27. Principal focus is also known as focal point.

  28. 4 x 2 = 8
  29. The radius of curvature of a spherical mirror is 20 cm. Find its focal length.

  30. If two plane mirrors are inclined to each other at an angle of 90°, find the number of images formed.

  31. Who founded the Book "On Burning Mirrors"?

  32. What is the value of velocity of light in air?

  33. 3 x 3 = 9
  34. What is called a spherical mirror?

  35. Define focal length?

  36. State the laws of reflection.

  37. 2 x 5 = 10
  38. What is reflection? Write short notes on regular and irregular reflection?

  39. What is dispersion? Explain in detail.

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