A microscope is focused on a mark on a piece of paper and then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again?

Question

A microscope is focused on a mark on a piece of paper and then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again? (A) 1 cm upward (B) 4.5 cm downward (C) 1 cm downward (D) 2 cm upward

Tardigrade Admin · Accepted Answer

Apparent depth of mark as seen through a glass slab of thickness

x

and refractive index

μ

,
is Apparent depth

= \frac{Real depth}{Refractive index}

or

x = \frac{x}{μ} = \frac{3}{1.5} = 2 c m

As image appears to be raised by

1 c m

,
therefore, microscope must be moved upward by

1 c m

Q. A microscope is focused on a mark on a piece of paper and then a slab of glass of thickness 3cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again?

1 cm upward

4.5 cm downward

1 cm downward

2 cm upward

Apparent depth of mark as seen through a glass slab of thickness x and refractive index μ , is Apparent depth =Refractive indexReal depth​ or x=μx​=1.53​=2cm As image appears to be raised by 1cm, therefore, microscope must be moved upward by 1cm

Q. A microscope is focused on a mark on a piece of paper and then a slab of glass of thickness $3 c m$ and refractive index $1.5$ is placed over the mark. How should the microscope be moved to get the mark in focus again?

Apparent depth of mark as seen through a glass slab of thickness $x$ and refractive index $μ$ ,
is Apparent depth $= \frac{Real depth}{Refractive index}$
or $x = \frac{x}{μ} = \frac{3}{1.5} = 2 c m$
As image appears to be raised by $1 c m$ ,
therefore, microscope must be moved upward by $1 c m$