﻿ A tank contains a slab of glass 8 cm thick and of refractive index 1.6. Above this is a depth of 4.5 cm of an oil and upon this floats a layer of water 6 cm thick and of refractive index 4/3. To an observer looking down from above, a mark at the bottom of the glass slab appears to be raised up to position 6 cm from the bottom of the slab. The refractive index of oil is : Kaysons Education

# A Tank Contains A Slab Of Glass 8 Cm Thick And Of Refractive Index 1.6. Above This Is A Depth Of 4.5 Cm Of An Oil And Upon This Floats A Layer Of Water 6 Cm Thick And Of Refractive Index 4/3. To An Observer Looking Down From Above, A Mark At The Bottom Of The Glass Slab Appears To Be Raised Up To Position 6 Cm From The Bottom Of The Slab. The Refractive Index Of Oil Is

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## Question

### Solution

Correct option is

1.5

O is the mark at the bottom of the glass slab (fig.). Since the boundaries of the media are parallel, the total shift of the mark O is equal to the shift due to each of the three media. Let  be the refractive index of the oil.

Total apparent shift (OI) = shift due to glass + shift due to oil + shift due to water

But                  OI = 6 cm (given). Hence

or

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