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SolveItNCERT · CBSE · NEET

NCERT Exemplar · Class 10 Science The Human Eye and the Colourful World

30 questions · 30 still being checked

Multiple Choice Questions 11–14 (part 2 of 4)

  1. Exercise 11

    The bluish colour of water in deep sea is due to
    (a)
    the presence of algae and other plants found in water
    (b)
    reflection of sky in water
    (c)
    scattering of light
    (d)
    absorption of light by the sea

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    NCERT’s answer
    (c)
    (c) scattering of light.Water molecules scatter the shorter blue wavelengths more strongly than longer ones; the scattered blue light reaching the eye gives deep water its colour. \[I_{scatter}\propto\frac{1}{\lambda^4}\ \Rightarrow\ \text{blue scattered most strongly} \]

  2. Exercise 12

    When light rays enter the eye, most of the refraction occurs at the
    (a)
    crystalline lens
    (b)
    outer surface of the cornea
    (c)
    iris
    (d)
    pupil

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    NCERT’s answer
    (b)
    (b) outer surface of the cornea.The air-cornea interface carries the largest change in refractive index in the eye; the fluids and lens beyond it are already close to its index.\[n_1\sin\theta_1=n_2\sin\theta_2,\qquad n_{air}=1.00\ \xrightarrow{\ \Delta n\ \text{largest}\ }\ n_{cornea}\approx1.38 \]

  3. Exercise 13

    The focal length of the eye lens increases when eye muscles
    (a)
    are relaxed and lens becomes thinner
    (b)
    contract and lens becomes thicker
    (c)
    are relaxed and lens becomes thicker
    (d)
    contract and lens becomes thinner

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    (a)
    (a) are relaxed and lens becomes thinner.Relaxed ciliary muscles let the taut suspensory ligaments pull the lens flat; a thinner lens converges light less, so its focal length increases.\[\text{muscles relaxed} \Rightarrow \text{lens thinner} \Rightarrow P\downarrow \] \[P=\frac{1}{f} \Rightarrow f\uparrow \]

  4. Exercise 14

    Which of the following statement is correct?
    (a)
    A person with myopia can see distant objects clearly
    (b)
    A person with hypermetropia can see nearby objects clearly
    (c)
    A person with myopia can see nearby objects clearly
    (d)
    A person with hypermetropia cannot see distant objects clearly

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    NCERT’s answer
    (c)
    (c) A person with myopia can see nearby objects clearly.A myopic eye is too long or too converging, so a distant image forms before the retina; a near image still lands on it.