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. ${10}^{°}$

A beam of light from a source L is incident normally on a plane mirror fixed at a certain distance x from the source. The beam is reflected back as a spot on a scale placed just above the source L. When the mirror is rotated through a small angle $\theta$, the spot of light is found to move through a distance y on the scale. The angle $\theta$ is given by 

1. $\frac{y}{2x}$

2. $\frac{y}{x}$

3. $\frac{x}{2y}$

4. $\frac{x}{y}$

An air bubble in a glass slab with refractive index 1.5 (near normal incidence) is 5 cm deep when viewed from one surface and  3 cm deep when viewed from the opposite face. The thickness (in cm) of the slab is

1. 8           

2. 10

3. 12         

4. 16

A person can see clearly objects only when they lie between 50 cm and 400 cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use will be-

1. convex, +2.25 diopter

2. concave, - 0.25 diopter

3. concave, - 0.2 diopter

4. convex, + 0.15 diopter

A linear aperture whose width is 0.02 cm is placed immediately in front of a lens of focal length 60 cm. The aperture is illuminated normally by a parallel beam of wavelength $5\times {10}^{-5}$ cm. The distance of the first dark band of the diffraction pattern from the centre of the screen is

1. 0.10 cm             

2. 0.25 cm 

3. 0.20 cm             

4. 0.15 cm

An astronomical telescope has an objective and eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective, the lenses must be separated by a distance of :
1. 46.0 cm

2. 50.0 cm  

3. 54.0 cm

4. 37.3 cm 

A beam of light consisting of red, green and blue colours is incident on a right angled prism. The refractive index of the material of the prism for the above red, green and blue wavelengths are 1.39, 1.44 and 1.47, respectively.


The prism will

1. separate the blue colour part from the red and green colours

2. separate all the three colours from one another

3. not separate the three colours at all

4. separate the red colour part from the green and blue colours

If the focal length of the objective lens is increased, then magnifying power of :

1. microscope will increase but that of telescope decrease

2. microscope and telescope both will increase

3. microscope and telescope both will decrease

4. microscope will decrease but that of telescope will increase