A diver in a swimming pool wants to signal his distress to a person lying on the edge of the pool by flashing his waterproof flash light:

(1) he must direct the beam vertically upwards.

(2) he has to direct the beam horizontally.

(3) he has to direct the beam at an angle to the vertical which is slightly less than the critical angle of incidence for total internal reflection.

(4) he has to direct the beam at an angle to the vertical which is slightly more than the critical angle of incidence for internal reflection.

A thin convergent glass lens ($\mu$_g = 1.5) has a power of + 5.0 D. When this lens is immersed in a liquid of refractive index $\mu$₁ it acts as a divergent lens of focal length 100 cm. The value of $\mu$₁ must be

(1) 4/3           

(2) 5/3         

(3) 2           

(4) 7/3

An air bubble in glass slab ($\mu$ = 1.5) when viewed from one side appears to be at 6 cm and from opposite side 4 cm. The thickness of glass slab is

(1) 10 cm                       

(2) 6.67 cm

(3) 15 cm                       

(4) none of these

Convergence of concave mirror can be decreased by dipping in

(1) Water

(2) Oil

(3) Both

(4) None of these

The reflected light wave and incident light wave differ each other by a phase angle of ${180}^0$, when

1. Light enters into glass from air

2. Light enters into air from glass

3. Light enters into glass from diamond

4. Light enters into water from glass

A graph is plotted between the angle of deviation $\delta$ in a triangular prism and the angle of incidence as shown in the figure. Refracting angle of the prism is: 

 
1. \(28^\circ\)
2. \(48^\circ\)
3. \(36^\circ\)
4. \(46^\circ\)

Minimum distance between real object and image produced by a concave mirror of focal length 20 cm is:

(1) 80 cm

(2) zero

(3) 20 cm

(4) 40 cm

A prism of refracting angle $30°$, has one of the refracting faces polished. A beam of light incident on the other refracting face with i = $60°$ will retrace its path, if the refractive index of prism would be

1.  $\sqrt{2}$

2.  $\sqrt{3}$

3.  $\sqrt{5}$

4.  $\sqrt{7}$

A convex mirror of focal length \(20~\text{cm}\) forms an image that is a quarter of the object's size. The distance of the object from the mirror is:
1. \(50~\text{cm}\)
2. \(-60~\text{cm}\) 
3. \(-40~\text{cm}\) 
4. \(-70~\text{cm}\)