A microscope is focussed on an ink mark on the top of a table. If we place a glass slab of $3$ cm thick on it, how should the microscope be moved to focus the ink spot again? The refractive index of glass is $1.5$ .

2

cm upwards

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2

cm downwards

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1

cm upwards

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1

cm downwards

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Solution

The correct option is A $1$ cm upwards
Given,
The refractive index of the glass is $n = 1.5$
The thickness of the glass slab is $h_{o} = 3$ cm

Refractive index is given as:
$n = \frac{h_{o}}{h_{i}}$

$1.5 = \frac{3}{h_{i}}$

$h_{i} = \frac{3}{1.5} = 2 c m$

So, the microscope needs to be shifted upwards by:
$h^{'} = 3 - 2 = 1 c m$ upwards.

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A microscope is focussed on an ink mark on the top of a table. If we place a glass slab of 3cm thick on it, how should the microscope be moved to focus the ink spot again? The refractive index of glass is 1.5.

The correct option is A 1cm upwardsGiven, The refractive index of the glass is n=1.5The thickness of the glass slab is ho=3cmRefractive index is given as:n=hohi1.5=3hihi=31.5=2 cmSo, the microscope needs to be shifted upwards by: h′=3−2=1 cm upwards.

A microscope is focussed on an ink mark on the top of a table. If we place a glass slab of $3$ cm thick on it, how should the microscope be moved to focus the ink spot again? The refractive index of glass is $1.5$ .