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A microscope is focussed on an ink mark ...

A microscope is focussed on an ink mark on th 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.

A

2 cm upwards

B

2 cm downwards

C

1 cm upwards

D

1 cm downwards

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