CBSE Class 10 Science 2023 Outside Delhi Set 1

Question : 25

Total: 39

A light ray enters from medium A to medium B as shown in the figure.

(a) Which one of the two media is denser w.r.t. other medium? Justify your answer.
(b) If the speed of light in medium A is va and in medium B is vb, what is the refractive index of B with respect to A.
OR
(a) A ray of light starting from diamond is incident on the interface separating diamond and water. Draw a labelled ray diagram to show the refraction of light in this case
(b) Absolute refractive indices of diamond and water are 2.42 and 1.33 respectively. Find the value of refractive index of water w.r.t. diamond.

Solution:

(a) The ray in medium B is moving towards normal when it enters from medium A. Hence, medium B is optically denser than medium A. This means that the refractive index of medium B with respect to refractive index of medium A will be greater than 1.
(b) Speed of light in rarer medium A(va) is greater than the speed of light in denser medium B(vb) i.e., va>vb
Thus, refractive index of B relative to A,
‌n=va∕vb
⇒n>1
OR

(b) Refractive index of water w.r.t. air is =1.33 Similarly refractive index of diamond w.r.t. air is =2.4
So, Refractive index of water with respect to diamond is =‌

1.33

2.4

=0.55

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