A plano-convex lens when silvered in the plane side behaves like a concave mirror of

focal length 30 cm. However, when silvered on the convex side it behaves like a concave

mirror of focal length 10 cm. Then the refractive index of its material will be 

1. 3.0                               

2. 2.0

3. 2.5                               

4. 1.5

A ray of light travels from an optically denser to rarer medium. The critical angle for the

two media is C. The maximum possible deviation of the ray will be

1. $\left(\frac{\mathrm{\pi }}{2}-C\right)$                         

2. 2C

3. $\mathrm{\pi }-2\mathrm{C}$                             

4. $\mathrm{\pi }-\mathrm{C}$

A concave mirror is placed on a horizontal table with its axis directed vertically upwards. Let O be the pole of the mirror and C is its centre of curvature. A point object is placed at C. It has a real image, also located at C. If the mirror is now filled with water, the image will be :

1. Real, and will remain at C

2. Real, and located at a point between C and $\infty$

3. Virtual and located at a point between C and O

4. Real, and located at a point between C and O

A room (cubical) is made of mirrors. An insect is moving along the diagonal on the floor

such that the velocity of image of insect on two adjacent wall mirrors is $10 cm{s}^{-1}$. The

velocity of image of insect in ceiling mirror is

1. 10 $cm{s}^{-1}$                           

2. 20 $cm{s}^{-1}$

3. $\frac{10}{\sqrt{2}}cm{s}^{-1}$                          

4. $10\sqrt{2}cm{s}^{-1}$

Figure shows a cubical room ABCD with the wall CD as a plane mirror. Each side of the

room is 3m. We place a camera at the midpoint of the wall AB. At what distance should

the camera be focussed to photograph an object placed at A

1. 1.5 m                                     

2. 3 m

3. 6 m                                         

4. More than 6 m

If an object moves towards a plane mirror with a speed v at an angle $\theta$ to the perpendicular to the plane of the mirror, find the relative velocity between the object and the image

1. v                                           

2. 2v

3. 2v cos $\theta$                                    

4. 2v sin $\theta$

A plane mirror is placed at the bottom of the tank containing a liquid of refractive index $\mu$. P is a small object at a height h above the mirror. An observer O vertically above P outside the liquid sees P and its image in the mirror. The apparent distance between these two will be-

1. $2\mu h$                                           

2.  $\frac{2h}{\mu }$

3. $\frac{2h}{\mu -1}$                                         

4.  $h\left(1+\frac{1}{\mu }\right)$ 

To an astronaut in a spaceship, the sky appears:

1. Black                   

2. White

3. Green                 

4. Blue

A thin prism having refracting angle ${10}^{°}$ is made of glass of refractive index 1.42. This prism is combined with another thin prism of glass of refractive index 1.7. This combination produces dispersion without deviation. The refracting angle of second prism should be 

1. $4^{°}$

2. $6^{°}$

3. $8^{°}$

4. ${10}^{°}$