A travelling microscope is focused on a mark on a table. If a glass block of thickness 18.0cm is placed on the mark by how many centimeters will the microscope be moved upwards so as to focus the mark once again? [refractive index of glass = 1.5]
-
A.
27cm -
B.
24cm -
C.
9cm -
D.
6cm
Correct Answer: Option D
Explanation
Apparent depth = (frac{text{thickness}}{text{refractive index}})
= (frac{18}{1.5} = 12cm)
Upward adjustment = 18 – 12
= 6cm