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Year 11 Science — Reflection and refraction of light

Apply the New Cartesian Sign Convention to the mirror and lens formulae, work out magnification and the power of a lens, and read a refractive index for what it says about the speed of light.

Name: ________________________

  1. 1.What is the SI unit of the power of a lens? Answer with one word.

  2. 2.Match each medium to its refractive index as the chapter's table gives it.

    • Water
    • Kerosene
    • Crown glass
    • Diamond
    • 1.44
    • 1.52
    • 2.42
    • 1.33

  3. 3.For that same lens the image distance is v = +30 and the object distance is u = -15. Magnification for a lens is m = v/u. What is m? Answer with a number, sign included.

  4. 4.A concave mirror is drawn below with its principal axis. The dot at the far left is the centre of curvature and the dot at the mirror is the pole. Tap the principal focus.

    Write the number of the part.

    123

  5. 5.The refractive index of water is 1.33. What does that number say?

    • a) Water is 1.33 times as dense as air
    • b) A ray bends through 1.33 degrees on entering water
    • c) Light travels 1.33 times as fast in air as it does in water
    • d) Light travels 1.33 times as fast in water as it does in air

  6. 6.An optician puts two lenses in contact in a testing frame, one of power +2.0 D and one of +0.25 D. What is the power of the combination?

    • a) +2.0 D
    • b) +1.125 D
    • c) +2.25 D
    • d) +0.5 D

  7. 7.Sort each arrangement by the kind of image it gives.

    Groups: Real and inverted · Virtual and erect

    • Object anywhere in front of a convex mirror
    • Object beyond the centre of curvature of a concave mirror
    • Object between the pole and the focus of a concave mirror
    • Object between the centre of curvature and the focus of a concave mirror
    • Object at the centre of curvature of a concave mirror

  8. 8.Under the New Cartesian Sign Convention, why does the object distance come out negative?

    • a) The object is closer to the mirror than the image is
    • b) The object is below the principal axis
    • c) The object is placed to the left of the mirror, and distances to the left of the pole count negative
    • d) Object distances are measured from the centre of curvature

Answer key — Year 11 Science — Reflection and refraction of light

  1. 1.
    • dioptre
    • diopter
  2. 2. Water → 1.33; Kerosene → 1.44; Crown glass → 1.52; Diamond → 2.42
  3. 3. -2
  4. 4. 2 — The principal focus
  5. 5. c) Light travels 1.33 times as fast in air as it does in water
  6. 6. c) +2.25 D
  7. 7. Object beyond the centre of curvature of a concave mirror → Real and inverted; Object at the centre of curvature of a concave mirror → Real and inverted; Object between the centre of curvature and the focus of a concave mirror → Real and inverted; Object between the pole and the focus of a concave mirror → Virtual and erect; Object anywhere in front of a convex mirror → Virtual and erect
  8. 8. c) The object is placed to the left of the mirror, and distances to the left of the pole count negative