Ray Optics and Optical Test

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Ray Optics and Optical Test - 13

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Weekly Quiz Competition

Question 1
1 / -0

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

A
a screw gauge provided on the microscope

B
a standard laboratory scale

C
a vernier scale provided on the microscope

D
a meter scale provided on the microscope

Solution

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 2
1 / -0

The distance CP is the :

A
Center of curvature

B
Radius of curvature

C
Focal length

D
None of these

Solution

The distance CP is the radius of curvature.
Question 3
1 / -0

A printed page is seen through a glass slab place on it. The printed words appear raised. This is due to:

A
Refraction at the upper surface of the slab

B
Refraction at the lower surface of the slab

C
Partial reflection at the upper surface of the slab

D
Partial reflection at the lower surface of the slab

Solution

Refraction at the upper surface of the slab.
Question 4
1 / -0

The instrument that is based on the principle that when an object is placed between first principal focus and the optic centre of convex lens, an upright, virtual and enlarged image on the same side of the object is formed, is:

A
Telescope

B
Projector

C
Camera

D
Simple microscope

Solution

In astronomical telescope 2 convex lens called eyepiece and objective lens are used and object is placed before eyepiece lens, such that final image inverted, a camera and eye also form inverted image on the screen. Whereas simple microscope gives an erect, virtual and enlarged image of the object placed between first principal focus and the optic nerve of the convex lens.
In a projector, the image formed is real, inverted magnified on the other side of the lens. This inverted image is again inverted by the film.
Question 5
1 / -0

The apparent vertical shift of the image of a coin placed at the bottom of a water tank having constant depth of water is proportional to (given refractive index of water =$$\mu$$).

A
$$\mu $$

B
$$\cfrac{1}{\mu }$$

C
$$\mu -1$$

D
$$\mu +1$$

Solution

Answer is B.

The apparent vertical shift is given by the equation $$AD=\cfrac { RD }{ \mu } ,\quad that\quad is,\quad \mu =\cfrac { RD }{ AD } $$, where AD is the apparent vertical shift, RD is the real depth of the tank and n is the refractive index of the denser medium, that is, water.
As real depth and refractive index is going to be constant always, the apparent shift or depth will be independent of viewing angle.
From the above equation, we can see that the apparent vertical shift is inversely proportional to the refractive index. That is, $$\cfrac { 1 }{ \mu } $$.
Question 6
1 / -0

A pencil dipped partially in water appears bent because of :

A
reflection at water surface

B
diffraction at water surface

C
refraction at water surface

D
water is flowing

Solution

Refraction is a phenomenon in which a light ray incident on a surface separating two transparent media bends at the change of medium.
Snell's law gives the relation between angle of incidence and refraction and the Refractive index of the respective medium.
$${ \mu }_{ 1 }\sin { \left( i \right) } ={ \mu }_{ 2 }\sin { \left( r \right)}$$
where, i, r are the angles of incidence and refraction respectively.
Question 7
1 / -0

The phenomenon due to which a ray of light .......... from its path while travelling from one optical medium to another optical medium is called refraction.

A
reflected

B
deviates

C
normally

D
less

Solution

Deviates
Refraction is a phenomenon in which when a ray passes from one medium to another it bends away from its straight-line path due to the difference in optical densities or refractive indices of the two mediums. This bending is known as deviation.
Question 8
1 / -0

In the white light of sun, maximum scattering by the air molecules present in the earth's atmosphere is for:

A
red colour

B
yellow colour

C
green colour

D
blue colour

Solution

$${\Large\underline{\textbf{Concept Used:}}}$$

$${\large{\textbf{Rayleigh Scattering}}}$$
In the process of scattering, light rays are absorbed by the particles of a medium and remitted in random directions. When white light passes through a medium, different wavelengths are scattered differently.
Shorter the wavelength, the higher the chances of the light being scattered due to its high frequency. According to Rayleigh's Theory, the intensity of scattered light in a medium is related to the wavelength as,
$$I \propto \frac{1}{\lambda ^4}$$

$${\Large\underline{\textbf{Correct Answer: D}}}$$

$${\Large {\textbf{Explanation}}}$$
$$\bullet$$ By Rayleigh's Criterion intensity of scattered light is given by, $$I \propto \frac{1}{\lambda ^4}$$
$$\Rightarrow$$ Intensity of scattered light is more for smaller wavelengths of light.
$$\bullet$$ In the visible spectrum, the $$blue$$ side of the spectrum has a $$smaller \ wavelength$$ compared to the red side. Hence blue light is $$scattered \ more$$ by air molecules present in earth's atmosphere.
Question 9
1 / -0

Blue colour of sky is due to:

A
scattering.

B
absorption.

C
reflection.

D
refraction.

Solution

Blue light is scattered the most. Hence, as sunlight travels the earth, most of the blue colour is scattered and hence spread. This causes the sky to appear blue in the day.
Question 10
1 / -0

Magnification of an optical instrument is expressed in:

A
m

B
$$m^{-1}$$

C
D

D
It has no unit

Solution

$$\text{Magnification} = \cfrac{\text{Image Height}}{\text{Object Height}}$$
because unit of image height and object height is same hence unit of magnification is none because it is a constant number. So, it has got to unit.

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Re-Attempt Weekly Quiz Competition

Ray Optics and Optical Test - 13

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Ray Optics and Optical Test - 13

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Question 1

a screw gauge provided on the microscope

a standard laboratory scale

a vernier scale provided on the microscope

a meter scale provided on the microscope

Solution

Question 2

Center of curvature

Radius of curvature

Focal length

None of these

Solution

Question 3

Refraction at the upper surface of the slab

Refraction at the lower surface of the slab

Partial reflection at the upper surface of the slab

Partial reflection at the lower surface of the slab

Solution

Question 4

Telescope

Projector

Camera

Simple microscope

Solution

Question 5

$$\mu $$

$$\cfrac{1}{\mu }$$

$$\mu -1$$

$$\mu +1$$

Solution

Question 6

reflection at water surface

diffraction at water surface

refraction at water surface

water is flowing

Solution

Question 7

reflected

deviates

normally

less

Solution

Question 8

red colour

yellow colour

green colour

blue colour

Solution

Question 9

scattering.

absorption.

reflection.

refraction.

Solution

Question 10

m

$$m^{-1}$$

D

It has no unit

Solution

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