Question 1

The focal length of a lens of refractive index  \mu   is  f . If the lens is immersed in a liquid of refractive index  \mu   then the focal length of lens is

Accepted Answer

\dfrac{1}{f} = (n-1) (\dfrac{1}{R_1}- \dfrac{1}{R_2})  where,  n  is refractive index of lens material with respect to its surrounding mediumIf lens is immersed in the liquid of refractive index equal to its own then  n=1  and hence above equation becomes:  \dfrac{1}{f} = 0 \Rightarrow f = \infty

Question 2

A convex glass lens is immersed in water. Compared to the power in air, its power in water will :

Accepted Answer

Power of a lens  =\dfrac{1}{f} Where  f   is the focal length of the lens.So, by lens maker formula \dfrac{1}{f}=\left ( \dfrac{\mu _{2}}{\mu _{1}}-1 \right )\left ( \dfrac{1}{R_{1}}-\dfrac{1}{R_{2}} \right ) As lens is dipped in water,  \mu  of the medium is increased from 1 to  \dfrac{4}{3}   (i.e. refractive index of water), so,  \dfrac{\mu_{2}}{\mu_{1}}  term decreases, so,  \left ( \dfrac{\mu_{2}}{\mu_{1}}-1 \right )  term decrease which leads to decrease of  \dfrac{1}{f}.  so, power  \left ( =\dfrac{1}{f} \right )  decreases.

Question 3

A glass slab is placed in the path of beam of convergent light. The point of convergence of light

Accepted Answer

As a glass has refractive index of 3/2 with respect to air, the convergent light will bend towards the normal in the glass and again bend away from the normal, but in the whole process the beam is displaced parallel to initial path as shown in figure and converge at a greater distance from the glass slab.

Question 4

What are the colours of the Sun observed most during sunrise/sunset and noon?

Accepted Answer

During sunrise and sunset the sun rays have to pass through a larger distance and also a greater thickness of air since it is low in the sky. At these positions, the sky looks orange-red colour because photons of red and orange light are least scattered through the atmosphere and are able to reach our eyes.

Question 5

Red light is used as danger signal because it is:

Accepted Answer

Red light is used as danger signal because it is having high wavelength, less scattering ,hence can travel larger distances.

Question 6

The line joining the pole and the centre of curvature of a mirror is called the :

Accepted Answer

The line joining the pole and the center of curvature of a mirror is called the principal axis.

Question 7

The relation between u, v and r is:

Accepted Answer

We know,  1/f = 1/u +1/v Or  2/r = 1/u +1/v Since radius of curvature is double the focal length. This leads to option A.

Question 8

An achromatic combination of lenses produce :

Accepted Answer

An achromatic combination of lenses provide deviation without dispersion. So, images are unaffected by variation of refractive index with wavelength. Hence correct option is C.

Question 9

An experiment is performed to find the refractive index of glass using a travelling microscope. In this experiment distances are measured by:

Accepted Answer

The travelling microscope moves horizontally on a main scale provided with the vernier scale provided with the microscope that's why, In a travelling microscope to find the refractive index of glass we measure distance by a vernier scale provided on the microscope.

Question 10

The distance CP is the :

Accepted Answer

The distance CP is the radius of curvature.

Ray Optics And Optical Instruments

Physics
1192 Views

The focal length of a lens of refractive index $μ$ is $f$ . If the lens is immersed in a liquid of refractive index $μ$ then the focal length of lens is

A convex glass lens is immersed in water. Compared to the power in air, its power in water will :

A glass slab is placed in the path of beam of convergent light. The point of convergence of light

What are the colours of the Sun observed most during sunrise/sunset and noon?

Red light is used as danger signal because it is:

The line joining the pole and the centre of curvature of a mirror is called the :

The relation between u, v and r is:

An achromatic combination of lenses produce :

An experiment is performed to find the refractive index of glass using a travelling microscope. In this experiment distances are measured by:

The distance CP is the :

Ray Optics And Optical Instruments

Physics 1192 Views

The focal length of a lens of refractive index μ is f. If the lens is immersed in a liquid of refractive index μ then the focal length of lens is

A convex glass lens is immersed in water. Compared to the power in air, its power in water will :

A glass slab is placed in the path of beam of convergent light. The point of convergence of light

What are the colours of the Sun observed most during sunrise/sunset and noon?

Red light is used as danger signal because it is:

The line joining the pole and the centre of curvature of a mirror is called the :

The relation between u, v and r is:

An achromatic combination of lenses produce :

An experiment is performed to find the refractive index of glass using a travelling microscope. In this experiment distances are measured by:

The distance CP is the :

Physics
1192 Views

The focal length of a lens of refractive index $μ$ is $f$ . If the lens is immersed in a liquid of refractive index $μ$ then the focal length of lens is