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]
- 27cm
- 24cm
- 9cm
-
6cm
The correct answer is: D
Explanation
Apparent depth = \(\frac{\text{thickness}}{\text{refractive index}}\)= \(\frac{18}{1.5} = 12cm\)
Upward adjustment = 18 - 12
= 6cm