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Question
The diagram shows the path of a ray of light through a rectangular glass block placed in a liquid of uniform density.

What should be the rate of the speed of light through the liquid to the speed through the glass so that there is no refraction of light at the boundaries of the glass block when the system is illuminated by the light of one colour?
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Solution
Since there is no refraction of light at the boundaries of the glass block, it is possible only when the speed of light through the liquid as well as through the block is the same. Hence the ratio between the speed of light through the liquid to the speed of light through glass must be 1 (one).
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