Question

When measuring the thickness of a glass slab using a travelling microscope, the microscope is focused on ______.

Options

• The pin placed on the glass slab

• The lower surface of the glass slab

• The upper surface of the glass slab

• The image of the pin through the glass slab

Answer 1

When measuring the thickness of a glass slab using a travelling microscope, the microscope is focused on the image of the pin through the glass slab.

Explanation:

In this experiment, the travelling microscope is focused on the image of the pin as seen through the glass slab. Due to refraction, the image of the pin appears to be at a position different from its actual position (apparent depth ≠ real depth), and this shift is used to determine the refractive index of the glass slab.