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NCERT Class 10 Science Light – Reflection and Refraction: In-text questions (page 150) Solutions

AI-written, checked on 23 Oct 2026

Solutions written by Shishya, checked — not the board's official answers

Step-by-step working for every question of In-text questions (page 150) in NCERT's Class 10 Science book, chapter “Light – Reflection and Refraction”, written by Shishya. Each question is in our own short words; open the NCERT chapter for the exact wording and figures.

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How these were checked: the solutions were drafted with AI and then read and corrected on 23 Oct 2026. Every numerical final answer is recomputed from the question's own numbers by a calculator check that runs before each release; proofs and explanations were read, not machine-checked. The NCERT textbook is the authority — if something here disagrees with it, follow the book.

Tap “why?” under a step to see the textbook rule it uses — from Shishya's fixed list of NCERT Class 9-10 rules, not written by AI for this page. A step without one has no rule from the list yet.

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  1. In-text (page 150) Q1

    A ray of light passes obliquely from air into water. Does it bend towards or away from the normal? Why?

    1. Water is optically denser than air: light travels more slowly in water.
    2. When light passes obliquely from a rarer medium into a denser one, it slows down and bends towards the normal.
    3. So the ray bends towards the normal on entering water.

    Answer: Towards the normal, because water is optically denser than air and light slows down in it.

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  2. In-text (page 150) Q2

    Light enters glass of refractive index 1.50 from air. Find its speed in the glass (speed in vacuum 3 × 10⁸ m/s).

    1. Refractive index n = speed of light in vacuum ÷ speed of light in the medium, so v = c ÷ n.
      why?

      Refractive index = speed of light in vacuum (or in the first medium) ÷ speed of light in the medium; the larger it is, the more slowly light travels there and the more it bends towards the normal on entering.

    2. v = (3 × 10⁸ m/s) ÷ 1.50.
    3. v = 2 × 10⁸ m/s.

    Answer: Speed of light in the glass = 2 × 10⁸ m/s

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  3. In-text (page 150) Q3

    From Table 9.3 (refractive indices), which medium has the highest and which the lowest optical density?

    Uses a figure printed in the NCERT book — open the chapter above to see it.

    1. Optical density goes with refractive index: the larger the refractive index, the denser the medium.
      why?

      Refractive index = speed of light in vacuum (or in the first medium) ÷ speed of light in the medium; the larger it is, the more slowly light travels there and the more it bends towards the normal on entering.

    2. In Table 9.3, diamond has the largest refractive index (2.42).
      why?

      Refractive index = speed of light in vacuum (or in the first medium) ÷ speed of light in the medium; the larger it is, the more slowly light travels there and the more it bends towards the normal on entering.

    3. Air has the smallest (1.0003).

    Answer: Highest optical density: diamond (2.42); lowest: air (1.0003).

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  4. In-text (page 150) Q4

    Using Table 9.3, in which of kerosene (1.44), turpentine (1.47) and water (1.33) does light travel fastest?

    Uses a figure printed in the NCERT book — open the chapter above to see it.

    1. Light travels fastest in the medium with the lowest refractive index, since v = c ÷ n.
      why?

      Refractive index = speed of light in vacuum (or in the first medium) ÷ speed of light in the medium; the larger it is, the more slowly light travels there and the more it bends towards the normal on entering.

    2. Refractive indices: water 1.33, kerosene 1.44, turpentine 1.47.
    3. Water has the lowest value, so light is fastest in water.

    Answer: Light travels fastest in water (n = 1.33).

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  5. In-text (page 150) Q5

    The refractive index of diamond is 2.42. What does this mean?

    1. Refractive index of a medium = speed of light in vacuum ÷ speed of light in the medium.
      why?

      Refractive index = speed of light in vacuum (or in the first medium) ÷ speed of light in the medium; the larger it is, the more slowly light travels there and the more it bends towards the normal on entering.

    2. n = 2.42 for diamond means light in vacuum is 2.42 times as fast as light in diamond.
    3. So light travels at about 3 × 10⁸ ÷ 2.42 ≈ 1.24 × 10⁸ m/s in diamond.

    Answer: Light travels 2.42 times slower in diamond than in vacuum (speed in vacuum ÷ speed in diamond = 2.42).

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Other exercises in this chapter

← Light – Reflection and Refraction: notes, practice and all exercises

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