An object is placed on the principal axis of a concave mirror at a distance of 1.5f ( f is the focal length). The image will be at:

1.  -3f

2. 1.5f

3. -1.5f

4.  3f

If the critical angle for total internal reflection from a medium to vacuum is $45°$, the velocity of light in the medium is: 
1. \(1.5\times10^{8}\) m/s
2. \(\frac{3}{\sqrt{2}}\times10^{8}\) m/s
3. \(\sqrt{2}\times10^{8}\) m/s
4. \(3\times10^{8}\) m/s

The power of a biconvex lens is 10 dioptre and the radius of curvature of each surface is 10 cm. The refractive index of the material of the lens is:
1.  $\frac{4}{3}$

2.  $\frac{9}{8}$

3.  $\frac{5}{3}$

4.  $\frac{3}{2}$

For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index -

1.  lies between 2 and $\sqrt{2}$

2.  is less than 1 

3.  is greater than 2 

4.  lies between $\sqrt{2}$ and 1

A rod of length 10 cm lies along the principal axis of concave mirror of focal length 10 cm in such a way that its end closer to the pole is 20 cm away from the mirror. The length of the image is -

1.  15 cm 

2.  2.5 cm 

3.  5 cm 

4.  10 cm 

A thin prism of angle 15º made of glass of refractive index ${\mathrm{\mu }}_1$ = 1.5 is combined with another prism of glass of refractive index ${\mathrm{\mu }}_2$ = 1.75. The combination of the prism produced dispersion without deviation. The angle of the second prism should be :
1. 5º
2. 7º
3. 10º
4. 12º

A converging beam of rays is incident on a diverging lens. Having passed through the lens the rays intersect at a point 15 cm from the lens on the opposite side. If the lens is removed the point where the rays meet will move 5 cm closer to the lens. The focal length of the lens is :

1. 5 cm
2. -10 cm
3. 20 cm
4. -30 cm

The speed of light in media M₁ and M₂ is 1.5 × 10⁸ m/s and 2.0 × 10⁸ m/s respectively. A ray of light enters from medium M₁ to M₂ at an incidence angle i. If the ray suffers total internal reflection, the value of i is -

1. Equal to or less than sin^–1 $\left(\frac{3}{5}\right)$

2. Equal to or greater than sin^–1 $\left(\frac{3}{4}\right)$

3. less than sin^–1$\left(\frac{2}{3}\right)$

4. Equal to sin^–1 $\left(\frac{2}{3}\right)$

A ray of light is incident on a 60º prism at the minimum deviation position. The angle of refraction at the first face (i.e. incident face) of the prism is:

1. 30º

2. 45º

3. 60º

4. zero

A plane-convex lens of unknown material and unknown focal length is given. With the help of a spherometer, we can measure the,