SolveIt is under development
SolveItNCERT · CBSE · NEET

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

30 questions · 30 still being checked

Multiple Choice Questions 1–10 (part 1 of 4)

  1. Exercise 1

    A person cannot see distinctly objects kept beyond 2\displaystyle 2 m. This defect can be corrected by using a lens of power
    (a)
    + 0.5\displaystyle 0.5 D
    (b)
    0.5\displaystyle 0.5 D
    (c)
    + 0.2\displaystyle 0.2 D
    (d)
    0.2\displaystyle 0.2 D

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (b)
    (b) \(\displaystyle -0.5\,\mathrm{D}\). The far point is $\displaystyle 2$ m, so a distant object's image must form there, virtual, on the same side. \[\frac{1}{f}=\frac{1}{v}-\frac{1}{u}=\frac{1}{-2\,\mathrm{m}}-0=-0.5\,\mathrm{m^{-1}} \] \[P=\frac{1}{f}=-0.5\,\mathrm{D} \] A concave lens -- myopia.

  2. Exercise 2

    A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his text book. Which of the following statements is correct?
    (a)
    The near point of his eyes has receded away
    (b)
    The near point of his eyes has come closer to him
    (c)
    The far point of his eyes has come closer to him
    (d)
    The far point of his eyes has receded away

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (a)
    (a) The near point has receded. He reads the board fine (far point normal) but not his book at reading distance -- near vision blurred \(\displaystyle \Rightarrow\) the near point has moved beyond $\displaystyle 25$ cm, the classic hypermetropia sign.

  3. Exercise 3

    A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident on the prism as shown in Figure 11.1. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky?
    (a)(i)
    (b)(ii)
    (c)(iii)
    (d)(iv)
    NCERT_Question_Class10_Science_Exemplar_Ch11_Q3

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (b)
    (b) (ii). \(\displaystyle \mu_V>\mu_R\Rightarrow\delta_V>\delta_R\): every colour bends toward the base, violet most. Base is up here, so top-to-bottom the exit band reads V, I, B, G, Y, O, R -- the 3rd band, blue, is the sky's colour.

  4. Exercise 4

    At noon the sun appears white as
    (a)
    light is least scattered
    (b)
    all the colours of the white light are scattered away
    (c)
    blue colour is scattered the most
    (d)
    red colour is scattered the most

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (a)
    (a) Light is least scattered. Overhead at noon, sunlight crosses the shortest atmospheric path, so little blue is scattered away and the sun looks white.

  5. Exercise 5

    Which of the following phenomena of light are involved in the formation of a rainbow?
    (a)
    Reflection, refraction and dispersion
    (b)
    Refraction, dispersion and total internal reflection
    (c)
    Refraction, dispersion and internal reflection
    (d)
    Dispersion, scattering and total internal reflection

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (c)
    (c) Refraction, dispersion and internal reflection: the light refracts and disperses on entering, reflects once off the back, refracts out. \[\sin C=\frac{1}{n}=\frac{1}{1.33}\;\Rightarrow\; C\approx 49^\circ \] \[i_{\text{back}}\approx 40^\circ<C\;\Rightarrow\;\text{partial reflection, not total} \]

  6. Exercise 6

    Twinkling of stars is due to atmospheric
    (a)
    dispersion of light by water droplets
    (b)
    refraction of light by different layers of varying refractive indices
    (c)
    scattering of light by dust particles
    (d)
    internal reflection of light by clouds

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (b)
    (b) Refraction by atmospheric layers of varying refractive index. Their density keeps fluctuating, so the starlight's path shifts and its apparent position and brightness flicker. \[n_1\sin\theta_1=n_2\sin\theta_2=n_3\sin\theta_3,\qquad n_1<n_2<n_3\;\Rightarrow\;\theta_1>\theta_2>\theta_3 \]

  7. Exercise 7

    The clear sky appears blue because
    (a)
    blue light gets absorbed in the atmosphere
    (b)
    ultraviolet radiations are absorbed in the atmosphere
    (c)
    violet and blue lights get scattered more than lights of all other colours by the atmosphere
    (d)
    light of all other colours is scattered more than the violet and blue colour lights by the atmosphere

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (c)
    (c) Violet and blue scatter more than all other colours. Air molecules scatter short wavelengths most strongly, so scattered blue light reaches the eye from every part of the sky.

  8. Exercise 8

    Which of the following statements is correct regarding the propagation of light of different colours of white light in air?
    (a)
    Red light moves fastest
    (b)
    Blue light moves faster than green light
    (c)
    All the colours of the white light move with the same speed
    (d)
    Yellow light moves with the mean speed as that of the red and the violet light

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (c)
    (c) All the colours of the white light move with the same speed.Air is non-dispersive: its refractive index is the same for every wavelength, so all colours travel at one speed. \[v=\dfrac{c}{n_{\text{air}}},\qquad n_{\text{air}}\ \text{same for every }\lambda \ \Rightarrow\ v_{red}=v_{green}=v_{violet} \]

  9. Exercise 9

    The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because among all other colours, the red light
    (a)
    is scattered the most by smoke or fog
    (b)
    is scattered the least by smoke or fog
    (c)
    is absorbed the most by smoke or fog
    (d)
    moves fastest in air

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (b)
    (b) is scattered the least by smoke or fog.Scattering falls sharply with wavelength; red has the longest visible wavelength, so it scatters least and travels farthest through haze. \[I_{scatter}\propto\frac{1}{\lambda^4},\qquad \lambda_{red}>\lambda_{blue} \ \Rightarrow\ I_{scatter,\,red}<I_{scatter,\,blue} \]

  10. Exercise 10

    Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?
    (a)
    Dispersion of light
    (b)
    Scattering of light
    (c)
    Total internal reflection of light
    (d)
    Reflection of light from the earth

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (b)
    (b) Scattering of light.Sunlight crosses a much longer atmospheric path at sunrise or sunset; blue light is scattered out along the way, leaving red light to reach the eye. \[I_{scatter}\propto\frac{1}{\lambda^4},\qquad \text{path length}\uparrow \ \Rightarrow\ \text{blue removed}\uparrow\ \Rightarrow\ \text{transmitted light reddish} \]