A microscope is focused on an ink mark. A glass plate is placed over the spot. To focus the spot, microscope is raised 1m. To focus scratch on upper surface it must be raised 2m further. The refractive index of glass is

1.33

1.33

0%

1.50

1.50

0%

1.62

1.62

0%

1.80

1.80

0%