Find the value of the angle of emergence from the prism given below for the incidence ray shown. The refractive index of the glass is $\sqrt{3}$.

1. $45°$

2. $90°$

3. $60°$

4. $30°$

A beam of light is incident vertically on a glass slab of thickness 1 cm, and refractive index 1.5. A fraction 'A' is reflected from the front surface while another fraction 'B' enters the slab and emerges after reflection from the back surface. Time delay between them is:
1.  10^-10 s
2.  5 × 10^-10 s
3.  10^-11 s
4.  5 × 10^-11 s