Question

A large glass slab `(µ = 5/3)` of thickness 8 cm is placed over a point source of light on a plane surface. It is seen that light emerges out of the top surface of the slab from a circular area of radius R cm. What is the value of R?

Options

• 6 cm

• 7 cm

• 8 cm

• 9 cm

Answer 1

6 cm

Explanation:

tanc = `"R"/8`

`5/3`sinc = 1 × sin90°

sinc = `3/5`

C = 37°

`3/4="R"/8`

R = 6 cm