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Class 10 Science — The human eye and the colourful 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.Sort each description by the defect of vision it belongs to.

    Groups: Myopia · Hypermetropia

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

  2. 2.White light passing through a prism comes out as a band of seven colours. What is this splitting called? Answer with one word.

  3. 3.Newton passed his spectrum through a second identical prism placed upside down, and got white light out again. What did that show him?

    • a) The second prism destroyed the colours
    • b) A prism can bend light but not split it
    • c) Sunlight is made up of the seven colours the first prism separated
    • d) The first prism had added colours to the light

  4. 4.Which colour bends the most as it passes through a prism, and which the least?

    • a) Violet the most, red the least
    • b) Green the most, violet the least
    • c) Red the most, violet the least
    • d) They bend equally, and separate by speed

  5. 5.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 convex lens, for near vision
    • c) A convex lens, for distant vision
    • d) A concave lens, for near vision

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

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

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

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

  8. 8.Why are danger signal lights red?

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

Answer key — Class 10 Science — The human eye and the colourful world

  1. 1. 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
  2. 2. dispersion
  3. 3. c) Sunlight is made up of the seven colours the first prism separated
  4. 4. a) Violet the most, red the least
  5. 5. a) A concave lens, for distant vision
  6. 6. b) There is too little scattering at that height
  7. 7. a) Relaxed, letting the lens thin out so its focal length increases
  8. 8. c) Red is scattered least by fog or smoke, so it carries its colour a long way