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.	\(46^\circ~\)

Three identical thin convex lenses are kept as shown in the figure. A ray passing through the lens is shown. The focal length of each lens is:

     
1. \(2\)
2. \(1.5\)
3. \(1.75\)
4. \(1.3\)

An astronomical telescope has angular magnification of \(20\) in its normal adjustment. Focal length of eyepiece is \(4\) cm. Distance between objective and eyepiece is:

If the space between two convex lenses of glass in the combination shown in the figure below is filled with water, then:
               

The focal lengths of the objective and eyepiece of a compound microscope are \(2​​\text{cm}\) and \(6.25​​\text{cm}\) respectively. An object \(AB\) is placed at a distance of \(2.5​​\text{cm}\) from the objective which forms the image \(A'B'\) as shown in the figure. The maximum magnifying power in this case, will be:
          

A concave lens of focal length \(25~\text{cm}\) produces an image \(\frac{1}{10}\text{th}\)$$ of the size of the object. The distance of the object from the lens is:

A convex mirror of focal length \(f\) forms an image which is \(\frac{1}{n}\) times the length of the object. The distance of the object from the mirror is:
1. \((n-1)f\)
2. \(\left( \frac{n-1}{n} \right)f\)
3. \(\left( \frac{n+1}{n} \right)f\)
4. \((n+1)f\)

A mark on the surface of the sphere \(\left(\mu= \frac{3}{2}\right)\) is viewed from a diametrically opposite position. It appears to be at a distance \(15~\text{cm}\) from its actual position. The radius of the sphere is:
1. \(15~\text{cm}\)
2. \(5~\text{cm}\)
3. \(7.5~\text{cm}\) 
4. \(2.5~\text{cm}\)

A light ray from the air is incident (as shown in the figure) at one end of glass fibre (refractive index \(\mu= 1.5\)) making an incidence angle of \(60^{\circ}\) on the lateral surface so that it undergoes a total internal reflection. How much time would it take to traverse the straight fibre of a length of \(1\) km?
   
1. \(3.33~\mu\text{s}\)
2. \(6.67~\mu\text{s}\)
3. \(5.77~\mu\text{s}\)
4. \(3.85~\mu\text{s}\)