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NCERT Exemplar · Class 10 Science Light - Reflection and Refraction

38 questions · 38 still being checked

Multiple Choice Questions 11–19 (part 2 of 4)

  1. Exercise 11

    A full length image of a distant tall building can definitely be seen by using
    (a)
    a concave mirror
    (b)
    a convex mirror
    (c)
    a plane mirror
    (d)
    both concave as well as plane mirror

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    NCERT’s answer
    (b)
    (b) A convex mirror always forms a diminished, erect image with a wide field of view, so the whole building is seen. \[0<m<1 \;\Rightarrow\; \text{full-length image of the building} \]

  2. Exercise 12

    In torches, search lights and headlights of vehicles the bulb is placed
    (a)
    between the pole and the focus of the reflector
    (b)
    very near to the focus of the reflector
    (c)
    between the focus and centre of curvature of the reflector
    (d)
    at the centre of curvature of the reflector

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    NCERT’s answer
    (b)
    (b) A source at the focus reflects into rays parallel to the axis: \[\text{source at } F \;\Rightarrow\; \text{reflected rays} \parallel \text{principal axis} \]A parallel beam throws light far without spreading -- what a torch or headlight needs.

  3. Exercise 13

    The laws of reflection hold good for
    (a)
    plane mirror only
    (b)
    concave mirror only
    (c)
    convex mirror only
    (d)
    all mirrors irrespective of their shape

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    NCERT’s answer
    (d)
    (d) At every point of incidence the normal is perpendicular to the surface there, whatever the shape. \[\angle i=\angle r \]Curvature only turns the normal; the law stays the same.

  4. Exercise 14

    The path of a ray of light coming from air passing through a rectangular glass slab traced by four students are shown as A, B, C and D in Figure 10.5. Which one of them is correct?
    (a)
    A (b) B (c) C (d) D NCERT_Question_Class10_Science_Exemplar_Ch10_Q14

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    NCERT’s answer
    (b)
    (b) B: the ray bends toward the normal on entering the denser glass, travels straight inside, then bends away from the normal on leaving, so the emergent ray is parallel to the incident ray.

  5. Exercise 15

    You are given water, mustard oil, glycerine and kerosene. In which of these media a ray of light incident obliquely at same angle would bend the most?
    (a)
    Kerosene
    (b)
    Water
    (c)
    Mustard oil
    (d)
    Glycerine

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    NCERT’s answer
    (d)
    (d) Glycerine — it bends the ray the most among the four liquids. \[n_{\text{glycerine}} > n_{\text{mustard oil}} > n_{\text{kerosene}} > n_{\text{water}} \] \[\sin r = \frac{\sin i}{n} \] A larger \(\displaystyle n\) gives a smaller \(\displaystyle r\) for the same \(\displaystyle i\), i.e. greater bending toward the normal.

  6. Exercise 16

    Which of the following ray diagrams is correct for the ray of light incident on a concave mirror as shown in Figure 10.6\displaystyle 10.6?
    (a)
    Fig. A
    (b)
    Fig. B
    (c)
    Fig. C
    (d)
    Fig. D
    NCERT_Question_Class10_Science_Exemplar_Ch10_Q16
    NCERT_Question_Class10_Science_Exemplar_Ch10_Q16_2
    NCERT_Question_Class10_Science_Exemplar_Ch10_Q16_3
    NCERT_Question_Class10_Science_Exemplar_Ch10_Q16_4
    NCERT_Question_Class10_Science_Exemplar_Ch10_Q16_5

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    NCERT’s answer
    (d)
    (d) Fig. D.\[\theta_i = \theta_r \quad \text{(law of reflection)} \] \[\text{ray} \parallel \text{axis} \;\xrightarrow{\text{concave mirror}}\; \text{reflected ray through } F \] A crosses between F and P, B at 2F (= C), C retraces its path.

  7. Exercise 17

    Which of the following ray diagrams is correct for the ray of light incident on a lens shown in Fig. 10.7\displaystyle 10.7?
    (a)
    Fig. A.
    (b)
    Fig. B.
    (c)
    Fig. C.
    (d)
    Fig. D.
    NCERT_Question_Class10_Science_Exemplar_Ch10_Q17
    NCERT_Question_Class10_Science_Exemplar_Ch10_Q17_2
    NCERT_Question_Class10_Science_Exemplar_Ch10_Q17_3
    NCERT_Question_Class10_Science_Exemplar_Ch10_Q17_4
    NCERT_Question_Class10_Science_Exemplar_Ch10_Q17_5

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    NCERT’s answer
    (a)
    (a) Fig. A.\[\text{ray through } F \;\xrightarrow{\text{convex lens}}\; \text{emergent ray} \parallel \text{axis} \] B bends up through the far F, C reverses, D goes straight.

  8. Exercise 18

    A child is standing in front of a magic mirror. She finds the image of her head bigger, the middle portion of her body of the same size and that of the legs smaller. The following is the order of combinations for the magic mirror from the top.
    (a)
    Plane, convex and concave
    (b)
    Convex, concave and plane
    (c)
    Concave, plane and convex
    (d)
    Convex, plane and concave

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    NCERT’s answer
    (c)
    (c) Concave, plane and convex.\[\text{concave } (|u|<|f|):\ |m|>1, \qquad \text{plane}:\ |m|=1, \qquad \text{convex}:\ |m|<1 \] Enlarged head: concave; same-size waist: plane; shrunk legs: convex.

  9. Exercise 19

    In which of the following, the image of an object placed at infinity will be highly diminished and point sized?
    (a)
    Concave mirror only
    (b)
    Convex mirror only
    (c)
    Convex lens only
    (d)
    Concave mirror, convex mirror, concave lens and convex lens

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    NCERT’s answer
    (d)
    (d) All four.\[\frac{1}{v}+\frac{1}{u}=\frac{1}{f}\quad(\text{mirror}) \] \[\frac{1}{v}-\frac{1}{u}=\frac{1}{f}\quad(\text{lens}) \] \[u\to\infty \;\Rightarrow\; \frac{1}{u}\to 0 \;\Rightarrow\; v=f \] Parallel rays meet, or appear to meet, at F in each case.