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Class 8 Science — Mirrors and lenses

Tell concave from convex for both mirrors and lenses, use the laws of reflection to find an angle, and say which of them gathers a beam and which spreads it.

Name: ________________________

  1. 1.You are handed a magnifying glass. Which kind of lens is it?

    • a) A concave lens
    • b) A plane lens
    • c) A spherical mirror
    • d) A convex lens

  2. 2.What does the image in a convex mirror look like, whatever the distance to the object?

    • a) Inverted and the same size as the object
    • b) Erect and larger than the object
    • c) Inverted and smaller than the object
    • d) Erect and smaller than the object

  3. 3.Each of these is a mirror doing a job. Sort them by which kind of mirror is used.

    Groups: Concave mirror · Convex mirror

    • A store's surveillance mirror
    • A road safety mirror at a bend
    • The reflector of a torch
    • A dentist's mirror
    • The side-view mirror of a vehicle

  4. 4.The angle between the normal and the incident ray has a three-word name. What is it?

  5. 5.A ray of light strikes a mirror at an angle of 35° to the normal. What is the angle of reflection, in degrees? Answer with a number.

  6. 6.The laws of reflection were worked out with a plane mirror. Which mirrors do they hold for?

    • a) Plane mirrors and nothing else
    • b) Curved mirrors, but not plane ones
    • c) Plane, concave and convex alike
    • d) Plane and concave mirrors, but not convex ones

  7. 7.Sunlight is directed onto a sheet of paper with a concave mirror, and the paper is moved until a small bright spot forms. What happens next, and why?

    • a) The spot spreads out, because a concave mirror scatters light
    • b) The paper cools down, because the mirror has taken the heat out of the light
    • c) The paper can start to burn, because the mirror has concentrated the sunlight onto that point
    • d) Nothing happens, because reflected light carries no heat

  8. 8.Why is a convex mirror, rather than a plane one, fitted as a vehicle's side-view mirror?

    • a) It shows the traffic behind the right way up, which a plane mirror cannot
    • b) It is cheaper to make than a plane mirror of the same size
    • c) It shows the traffic behind at a larger size
    • d) It shows a much wider area of the road behind

Answer key — Class 8 Science — Mirrors and lenses

  1. 1. d) A convex lens
  2. 2. d) Erect and smaller than the object
  3. 3. The reflector of a torch → Concave mirror; A dentist's mirror → Concave mirror; The side-view mirror of a vehicle → Convex mirror; A road safety mirror at a bend → Convex mirror; A store's surveillance mirror → Convex mirror
  4. 4. angle of incidence
  5. 5. 35
  6. 6. c) Plane, concave and convex alike
  7. 7. c) The paper can start to burn, because the mirror has concentrated the sunlight onto that point
  8. 8. d) It shows a much wider area of the road behind