If the absolute refractive indices of two media X and Y are 6/5 and 4/3 respectively, then the refractive index of Y with respect to X will be : (A) 10/9 (B) 9/10 (C) 9/8 (D) 8/9

ScienceCBSE Class 10 · Board exam 2025, set 31/2/1 · 1 mark · MCQ

CBSE Class 10 Science 2025: question 11

Set in the CBSE Class 10 board exam of 2025, paper 31/2/1, section A, question 11, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q11 · 1 mark · MCQLight – Reflection and Refraction

If the absolute refractive indices of two media X and Y are $\frac{6}{5}$ and $\frac{4}{3}$ respectively, then the refractive index of Y with respect to X will be :

(A) $\frac{10}{9}$
(B) $\frac{9}{10}$
(C) $\frac{9}{8}$
(D) $\frac{8}{9}$

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/2/1.

Hints

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

Hint 1

'Y with respect to X' means Y's index divided by X's.

Hint 2

Divide $\frac{4}{3}$ by $\frac{6}{5}$ .

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.

Refractive index of Y with respect to X: $n_{Y X} = \frac{n _{Y}}{n _{X}}$ .
$n_{Y X} = \frac{4/3}{6/5} = \frac{4}{3} \times \frac{5}{6} = \frac{20}{18} = \frac{10}{9}$
Answer: **(A) $\frac{10}{9}$ **.
1 mark

Answer: $\frac{10}{9}$ , option (A)

Where the marks are

Uses $n_{Y X} = n_{Y} / n_{X}$ to get $10/9$ , option (A) (1 mark)

Revise the chapter

Chapter: Light – Reflection and Refraction (notes, formulas, where marks are lost and every past question)
Topic: Refraction of Light and Refractive Index

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 31/2/1: every question, by section.

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CBSE Class 10 Science 2025: question 11

Hints

Step-by-step solution

Revise the chapter

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