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
Verified Correct Answer: D.
Physical Principles & Numerical Solution
Apparent depth = \(\frac{\text{thickness}}{\text{refractive index}}\)
= \(\frac{18}{1.5} = 12cm\)
Upward adjustment = 18 - 12
= 6cm
Source: Myschool Past Questions Archive (Record #34679)