Skip to content

The values of absolute… (Class 10 Science 2025, Q24)

questionbuddy.in/q/cbse-10-science-2025-31-5-1-q24-values-absolute-refractive-indices-kerosene

ScienceCBSE Class 10 · Board exam 2025, set 31/5/1 · 2 marks · Very short answer

CBSE Class 10 Science 2025: question 24

Set in the CBSE Class 10 board exam of 2025, paper 31/5/1, section B, question 24, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q24 · 2 marks · Very short answerLight – Reflection and Refraction

The values of absolute refractive indices of kerosene and water are 1.44 and 1.33 respectively. Compare the two media on the basis of their

  1. (a)

    optical density

    0 marks
  2. (b)

    mass density

    0 marks
  3. (c)

    relative speed of propagation of light.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/5/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

A larger refractive index means what about optical density?

Hint 2

Which liquid floats on the other? Use for the speed of light.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a) Optical density: kerosene () has a higher refractive index than water (), so kerosene is optically denser than water.

    ½ mark

  2. (b) Mass density: kerosene floats on water, so kerosene has a lower mass density than water.

    ½ mark

  3. (c) Speed of light: since , light travels slower in kerosene and faster in water ().

    ½ mark

  4. Inference: A medium that is optically denser need not have a greater mass density. Optical density and mass density are different properties.

    ½ mark

Answer: Kerosene: higher optical density, lower mass density, lower speed of light than water. Inference: an optically denser medium need not be denser in mass.

Where the marks are

  • Kerosene has higher optical density than water (½ mark)
  • Kerosene has lower mass density than water (½ mark)
  • Light travels slower in kerosene than in water (½ mark)
  • Infers that optical density does not mean mass density (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Light – Reflection and Refraction, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/5/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.