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A mark at the bottom of a bekar is focus...

A mark at the bottom of a bekar is focussed by a microscope .When water is poured in the beaker up to a height of`16`cm,the microscope has to be raised through a distance of`4`cm in order to bring the mark to focus again .Calculate the refractive index of water.

Text Solution

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Let `d` be the real depth of the water.The apparent depth will be `d//mu`.So the microscope has to be raised through a distance
`(d-(d)/(mu))=d(1-(1)/(mu))`
`d(1-(1)/(mu))=4 or 16(1-(1)/(mu))=4 :.mu=4//3`
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