A small bulb is placed at the bottom of a tank containing water to a depth of 80 cm. What is the area of the surface of water through which light from the bulb can emerge out? The Refractive index of water is 1.33. (Consider the bulb to be a point source.)

1. 5.22 $m^{\mathrm{2 \; \; }}$
2. 1.33 $m^2$
3. 2.61 $m^2$
4 1.30 $m^2$

A tank is filled with water to a height of \(12.5\) cm. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be \(9.4\) cm.  If water is replaced by a liquid of refractive index \(1.63\) up to the same height, by what distance would the microscope have to be moved to focus on the needle again?
1. \(1.73\) cm
2. \(1.98\) cm
3. \(1.01\) cm
4. \(1.11\) cm

A small pin fixed on a table top is viewed from above from a distance of \(50~\text{cm}\). By what distance would the pin appear to be raised if it is viewed from the same point through a \(15~\text{cm}\) thick glass slab held parallel to the table? (The Refractive index of glass is \(1.5\))
1. \(5~\text{cm}\)
2. \(3~\text{cm}\)
3. \(3.5~\text{cm}\)
4. \(4.5~\text{cm}\)

The refractive index of glass is 1.5. What is the speed of light in glass? 

1.\(2 \times 10^{8} m/s\)
2.\(3 \times 10^{8} m/s\)
3.\(1.5 \times 10^{8} m/s\)
4.\(2.2 \times 10^{8} m/s\)