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Physics · 2022 · 3 marks
CBSE 2022 · Region 2 · Set 1 · Q5
(a) State the conditions for total internal reflection to take place. (b) A tank is filled with a transparent liquid to height 'H'. A coin suspended…
(a)
State the conditions for total internal reflection to take place.
(b)
A tank is filled with a transparent liquid to height 'H'. A coin suspended by a thread in the liquid is gradually lowered till it touches the bottom. The apparent depth is determined corresponding to different positions of the coin.
(i)
Plot a graph showing variation of the apparent depth with the real depth of the coin.
(ii)
What is the physical significance of the slope of the graph ?
Marking-scheme solution
(a)
The conditions for total internal reflection to take place are:
(i)
The light should travel from denser to rarer medium.
(ii)
The angle of incidence should be greater than the critical angle for a given pair of media.
(b)(i)
(ii)
The slope will give $\displaystyle 1/\mu$ where $\displaystyle \mu$ is refractive index as per the graph above.
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