Question

When a glass slab of refractive index 1.5 is placed on a cross marked on paper, the cross appears to be raised by 2 cm. The thickness of the slab is ______.

Options

• 3 cm

• 4 cm

• 6 cm

• 8 cm

Answer 1

When a glass slab of refractive index 1.5 is placed on a cross marked on paper, the cross appears to be raised by 2 cm. The thickness of the slab is 6 cm.

Explanation:

Given, n = 1.5 and d = 2 cm

The apparent raised height (d) of the cross is related to the thickness (t) of the glass slab and its refractive index (n) by the formula:

d = `t(1 - 1/n)`

Rearranging to find (t):

t = `d/(1 - 1/n)`

= `2/(1 - 1/1.5)`

= `2/(1 - 2/3)`

= `2/(1/3)`

= 6 cm