# Solve this question

given, refractive index = 1.5

to find, RD (as the thickness of the glass block will be equal to its real depth)

Let, RD = x

AD = x - 7 (as the distance between the bottom of the glass slab and and apparent depth is given)

we know, refractive index = RD/AD

therefore, 1.5 = x/(x - 7)

1.5x - 10.5 = x

1.5x -x = 10.5

0.5x =10.5

x = 21 mm or 2.1 cm (as 1 cm = 10mm)

Regards

**
**