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Grade 10 Science — The human eye and the colorful world

Name the parts of the eye and what each does, tell myopia from hypermetropia and pick the lens that corrects each, and explain dispersion, twinkling and the blue of the sky by refraction and scattering.

Name: ________________________

  1. 1.You look up from a book to the far end of the street. What have the ciliary muscles just done?

    • a) Contracted, making the lens thicker so its focal length decreases
    • b) Contracted, letting the lens thin out so its focal length increases
    • c) Relaxed, letting the lens thin out so its focal length increases
    • d) Relaxed, making the lens thicker so its focal length decreases

  2. 2.Why are danger signal lights red?

    • a) Red is scattered least by fog or smoke, so it carries its color a long way
    • b) Red light travels faster through fog
    • c) Red is scattered most, so it spreads out further
    • d) Red is the color the eye is most sensitive to at night

  3. 3.For a young adult with normal vision, what are the near point and the far point?

    • a) About 2 m, and infinity
    • b) About 25 cm, and a few meters
    • c) About 25 cm, and infinity
    • d) Zero, and infinity

  4. 4.Someone needs both distant and near vision corrected and is given bi-focal lenses. What is in the upper portion?

    • a) A concave lens, for distant vision
    • b) A concave lens, for near vision
    • c) A convex lens, for near vision
    • d) A convex lens, for distant vision

  5. 5.Why does the sky look dark to a passenger flying very high up?

    • a) The air is colder and refracts less
    • b) There is too little scattering at that height
    • c) The window glass absorbs the blue light
    • d) The Sun is closer and outshines the sky

  6. 6.Why is a clear sky blue?

    • a) The sea reflects its color up into the sky
    • b) Fine particles and air molecules scatter short blue wavelengths more strongly than long red ones
    • c) Blue light travels faster through air than red light does
    • d) The atmosphere is made of a blue gas

  7. 7.Atmospheric refraction makes the Sun visible about 2 minutes before it actually rises, and keeps it visible about 2 minutes after it actually sets. How many extra minutes of sunlight is that in a day? Answer with a number.

  8. 8.Sort each description by the defect of vision it belongs to.

    Groups: Myopia · Hypermetropia

    • The near point is farther away than it should be
    • Cannot see distant objects distinctly
    • Cannot see nearby objects distinctly
    • The image of a distant object forms in front of the retina
    • Light from a close object is focussed behind the retina
    • The far point is nearer than infinity

Answer key — Grade 10 Science — The human eye and the colorful world

  1. 1. c) Relaxed, letting the lens thin out so its focal length increases
  2. 2. a) Red is scattered least by fog or smoke, so it carries its color a long way
  3. 3. c) About 25 cm, and infinity
  4. 4. a) A concave lens, for distant vision
  5. 5. b) There is too little scattering at that height
  6. 6. b) Fine particles and air molecules scatter short blue wavelengths more strongly than long red ones
  7. 7. 4
  8. 8. Cannot see distant objects distinctly → Myopia; The far point is nearer than infinity → Myopia; The image of a distant object forms in front of the retina → Myopia; Cannot see nearby objects distinctly → Hypermetropia; The near point is farther away than it should be → Hypermetropia; Light from a close object is focussed behind the retina → Hypermetropia