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Science · Textbook solutions

Light — Reflection and Refraction

Every solved example, exercise, and miscellaneous question — in the order the textbook teaches them. · 37 questions

9.2 Spherical Mirrors

4 q

Questions

Practice · 4
  1. IT 9.1 Q1
    Define the principal focus of a concave mirror.
  2. IT 9.1 Q2
    The radius of curvature of a spherical mirror is 20 cm. What is its focal length?
  3. IT 9.1 Q3
    Name a mirror that can give an erect and enlarged image of an object.
  4. IT 9.1 Q4
    Why do we prefer a convex mirror as a rear-view mirror in vehicles?

9.2.4 Mirror Formula and Magnification

4 q

Solved Examples

Worked · 2
  1. 9.2 Eg.1
    A convex mirror used for rear-view on an automobile has a radius of curvature of 3.00 m. If a bus is located at 5.00 m from this mirror, find the position, nature and size of the image.
  2. 9.2 Eg.2
    An object, 4.0 cm in size, is placed at 25.0 cm in front of a concave mirror of focal length 15.0 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and the size of the image.

Questions

Practice · 2
  1. IT 9.2 Q1
    Find the focal length of a convex mirror whose radius of curvature is 32 cm.
  2. IT 9.2 Q2
    A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front of it. Where is the image located?

9.3 Refraction of Light

5 q

Questions

Practice · 5
  1. IT 9.3 Q1
    A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?
  2. IT 9.3 Q2
    Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? The speed of light in vacuum is 3 × 10⁸ m s⁻¹.
  3. IT 9.3 Q3
    Find out, from Table 9.3, the medium having highest optical density. Also find the medium with lowest optical density.
  4. IT 9.3 Q4
    You are given kerosene, turpentine and water. In which of these does the light travel fastest? Use the information given in Table 9.3.
  5. IT 9.3 Q5
    The refractive index of diamond is 2.42. What is the meaning of this statement?

9.3.7-9.3.8 Lens Formula, Magnification and Power of a Lens

5 q

Solved Examples

Worked · 2
  1. 9.4 Eg.3
    A concave lens has focal length of 15 cm. At what distance should the object from the lens be placed so that it forms an image at 10 cm from the lens? Also, find the magnification produced by the lens.
  2. 9.4 Eg.4
    A 2.0 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 10 cm. The distance of the object from the lens is 15 cm. Find the nature, position and size of the image. Also find its magnification.

Questions

Practice · 3
  1. IT 9.4 Q1
    Define 1 dioptre of power of a lens.
  2. IT 9.4 Q2
    A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.
  3. IT 9.4 Q3
    Find the power of a concave lens of focal length 2 m.

Exercises

19 q
  1. Ex 9 Q1
    Which one of the following materials cannot be used to make a lens?
    1. A.
      Water
    2. B.
      Glass
    3. C.
      Plastic
    4. D.
      Clay
  2. Ex 9 Q2
    The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?
    1. A.
      Between the principal focus and the centre of curvature
    2. B.
      At the centre of curvature
    3. C.
      Beyond the centre of curvature
    4. D.
      Between the pole of the mirror and its principal focus
  3. Ex 9 Q3
    Where should an object be placed in front of a convex lens to get a real image of the size of the object?
    1. A.
      At the principal focus of the lens
    2. B.
      At twice the focal length
    3. C.
      At infinity
    4. D.
      Between the optical centre of the lens and its principal focus
  4. Ex 9 Q4
    A spherical mirror and a thin spherical lens have each a focal length of –15 cm. The mirror and the lens are likely to be
    1. A.
      both concave
    2. B.
      both convex
    3. C.
      the mirror is concave and the lens is convex
    4. D.
      the mirror is convex, but the lens is concave
  5. Ex 9 Q5
    No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be
    1. A.
      only plane
    2. B.
      only concave
    3. C.
      only convex
    4. D.
      either plane or convex
  6. Ex 9 Q6
    Which of the following lenses would you prefer to use while reading small letters found in a dictionary?
    1. A.
      A convex lens of focal length 50 cm
    2. B.
      A concave lens of focal length 50 cm
    3. C.
      A convex lens of focal length 5 cm
    4. D.
      A concave lens of focal length 5 cm
  7. Ex 9 Q7
    We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.
  8. Name the type of mirror used in the following situations. Support your answer with reason.
    Ex 9 Q8 (a)
    Headlights of a car.
  9. Name the type of mirror used in the following situations. Support your answer with reason.
    Ex 9 Q8 (b)
    Side/rear-view mirror of a vehicle.
  10. Name the type of mirror used in the following situations. Support your answer with reason.
    Ex 9 Q8 (c)
    Solar furnace.
  11. Ex 9 Q9
    One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
  12. Ex 9 Q10
    An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
  13. Ex 9 Q11
    A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.
  14. Ex 9 Q12
    An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
  15. Ex 9 Q13
    The magnification produced by a plane mirror is +1. What does this mean?
  16. Ex 9 Q14
    An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.
  17. Ex 9 Q15
    An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focussed image can be obtained? Find the size and the nature of the image.
  18. Ex 9 Q16
    Find the focal length of a lens of power – 2.0 D. What type of lens is this?
  19. Ex 9 Q17
    A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?