Optics

Question 1

The path of light is called ray of light group of these rays are called

Answer 1

Beam of light

Question 2

Some of the sources emit thier own light and they are called

Answer 2

Luminous object

Question 3

You make the light from a torch to fall on your eyes, will you able to see the object

Answer 3

No, we can see the object only when the light is made to fall on the object and the light reflected from the object is viewed by our eyes

Question 4

Properties of light

Answer 4

1 Light is a form of energy
2 light always travels along the straight line
3) light does not need any medium for propagation. it can even travel through vacuum
4) the speed of light in vacuum or air is 3*10^8 m/s
5) light is in the form of waves, it is characterized by a wavelength [lambda (h)] and frequency we which are related by the following equation; c =vh c - velocity of light
6 Different coloured light has different wavelength and frequency
7 among the visible lights, violet light has the lowest wavelength and red light has the highest wavelength
8 when light is incident on the interface between two media it is partly reflected and partly refracted

Question 5

Refraction of light

Answer 5

When a Ray of light travels from one transparent medium into another obliquely , the path of the light undergoes deviation. This deviation of race of light is called refraction.

Refraction take place due to the difference in the velocity of light in different media
The velocity of light is more in a rare medium and less In a denser medium

Question 6

Frist Law of refraction

Answer 6

The incident ray the refractory of light and the normal to the refracting surface all lie in the same plane

Question 7

Second law of refraction

Answer 7

The ratio of the sine of the angle of incidence and sign of the angle of refraction is equal to ratio of refractive indices of the two media. This law is also known as snell’s law
Sin i/ sin r=u2/u1

Question 8

_______ gives us an idea of how fast are how slow light travels in a medium(second law of refraction)

Answer 8

Refractive index

Question 9

Refractive index

Answer 9

The ratio of speed of light in vacuum(c) to the speed of light in a medium (v) is defined as refractive index (u) of the medium

u= c/v

Question 10

Second law of refraction

Answer 10

The speed of light in a medium is low if the refractive index of the medium is high and vice versa

When light travels from here then sir medium into a rare medium, the refracted ray is bent away from the normal drawn to the interface

When light travels from a rare medium into denser medium, the refractor ray is Bent toward the normal drawn to the interface

Question 11

If you have source of light produces a light of single colour it is known as

Answer 11

Monochromatic source

Question 12

Source of light produces a white light which contain light of different colour is known as

Answer 12

Composite source
Eg: Sunlight, Mercury vapour lamp

Question 13

Dispersion of light

Answer 13

When a beam of white light or composite lens light is refracted through any transparent media such as glass or water, it is split into its component colour. This phenomenon is called as dispersion of light

Question 14

The band of colors is termed as

Answer 14

Spectrum
The spectrum consists of VIBGYOR

Question 15

Why do we get the spectrum when white light is refracted by a transparent medium

Answer 15

This is because different coloured light are bent through different angles. that is the angle of refraction is different for different colour

angle of refraction is the smallest for red and highest for violet

Question 16

Assertion: snell’s law we know that the angle of refraction is determined in term of the refractive index of the medium

Answer 16

Hence, the refractive index of the medium is different for different coloured light. This indicates that the refractive index of a medium is dependent on the wavelength of the light

Question 17

scattering of light

Answer 17

When sunlight enters the earth’s atmosphere, the atom and molecule of different gases present in the atmosphere refract the light in all possible directions this is called as scattering of light

In this phenomenon the beam of light is redirected in all directions when it interacts with a particle of medium. The interacting particle of the medium is called scatterer

Question 18

Types of scattering

Answer 18

Elastic scattering
Inelastic scattering

Question 19

Elastic scattering

Answer 19

If the energy of incident beam of light and scattered beam of light are same then it is called as elastic scattering

Question 20

Inelastic scattering

Answer 20

If the energy of them incident beam of light and be the scatter the beam of light or not same then it is called inelastic scattering

Types
Rayleigh scattering
Mei scattering
Tyndall scattering
Raman scattering

Question 21

Rayleigh scattering

Answer 21

The scattering of light by the atom or molecules of the gas in the earth atmosphere is known as Rayleigh scattering

Question 22

Rayleigh scattering law

Answer 22

Rayleigh’s scattering law states that, the amount of scattering of light is inversely proportional to the 4th power of it wavelength
→ proportional
S →1/h⁴. h- wavelength

According to this law the shorter wavelength colours are scattered much more than the longer wavelength colours

Question 23

Scattering causes the sky to appear in blue colour

Answer 23

When sunlight passes through the atmosphere, the blue colour (shorter wavelength) is scattered to a greater extent than the red colour ( longer wavelength)

Question 24

The colour of the sun is red at sunrise and sunset

Answer 24

At sunrise and sunset the light rays from the sun have to travel long distance in the atmosphere then at noon. Hence, most of the blue lights are scatter away and only the red light which in get reached scatter reaches us

Question 25

Mei scattering

Answer 25

Mie scattering take place when the diameter of the scatterer is similar to or larger than the wavelength of the incident light. It is also an elastic scattering. The amount of catering is independent of wavelength Mie scattering is caused by pollen, dust, smoke, water droplets, and other particles in the lower portion of the atmosphere

Question 26

Mie scattering Is responsible for the white appearance of the clouds

Answer 26

When white light falls on the water drop, all the colours are equally scattered which together form the white light

Question 27

Tyndall scattering or Tyndall effect

Answer 27

The scattering of light rays by the colloidal particles in the colloidal solution is called Tyndall scattering or Tyndall effect

Question 28

When a beam of sunlight, enters into a dusty room through a window, then its path becomes visible to us

Answer 28

This is because, tiny dust particles present in the air of the room scatter the beam of light

Question 29

Colloid

Answer 29

Colloid is a microscopically small substance that is equally dispersed throughout another material Eg milk, ice cream, muddy water, smoke

Question 30

Raman's scattering

Answer 30

The interaction of light rays with the particles of pure liquid or transparent solids which leads to a change in wavelength or frequency

Question 31

In Raman scattering , when a parallel beam of ________ light passes through a gas or liquid or transparent solid, a part of light rays are scattered

Answer 31

Monochromatic or single colored

Question 32

In Raman scattering , when a parallel beam of monochromatic (single colored) light passes through a gas or liquid or transparent solid, a part of light rays are scattered

Answer 32

The scattered light contains some additional frequency or wavelength other than that of incident frequency or wavelengths. This is known as raman's catering or Raman effect

Question 33

The spectral lines having frequency equal to the incident ray frequency is called

Answer 33

Rayleigh line

Question 34

Spectral lines which are having frequencies other than the incident ray frequency are called

Answer 34

Raman line The line having frequency lower than the incident frequency is called stoke line The lines having frequently higher than the incident frequency are called anti stoke lines

Question 35

Lens bounded by whose spherical surface such that it is thicker at the centre than at the edge. A beam of light passing through it, is converged to a point

Answer 35

Convex or bi convex lens Convex lens are also called as converging lens

Question 36

Lens bounded by two spherical surfaces such that it is thinner at the centre than at the edges. A beam of light passing through it, is diverged spread out to a point

Answer 36

Concave or bi concave lens Concave lens is also called as diverging lens

Question 37

If one of the faces of a bi convex lens is plane, it is known as

Answer 37

Plano convex lens

Question 38

If one of the faces of a bi concave lens is plane, it is known as

Answer 38

Plano concave lens

Question 39

It is an optically transparent medium bounded by two spherical refracting surfaces or one plane and one spherical surface

Answer 39

Lens

Question 40

Images formed due to refraction through a convex and the concave lens

Answer 40

Rule1: when a Ray of light strike the convex or concave lens obliquely at its optical centre, it continuous to follow it path without any deviation Rule 2 when rays parallel to the principal Axis strikes a convex or concave lens the refracted ray are converged to(convex) or appears to diverge from (concave lens) the principal focus Rule 3 when a ray passing through (convex lens) or directed toward (concave lens) the principle focus strikes a convex or concave lens the refracted ray will be parallel to the principal axis

Question 41

Refraction through a convex lens When an object is placed at infinity

Answer 41

Images formed at principal focus The size of the images much smaller than that of the object

Question 42

Refraction through a convex lens When an object is placed behind the centre of curvature

Answer 42

Ya real and inverter image is formed between the centre of curvature and principle focus The size of the images smaller than that of object

Question 43

Refraction through a convex lens When when an object is placed at the centre of curvature

Answer 43

A real and inverted image is formed at the other centre of curvature The size of the image is the same as that of object

Question 44

Refraction through a convex lens When an object is placed in between the centre of curvature and principle focus

Answer 44

Real and inverted image is formed Behind the centre of curvature The size of the images bigger than the object

Question 45

Refraction through a convex lens When an object is placed at the focus

Answer 45

Real images is formed at infinity The size of the images much larger than that of the object

Question 46

Refraction through a convex lens When an object is placed in between principal focus and optical centre

Answer 46

Virtual images formed the size of the images larger than that of

Question 47

Application of convex lens

Answer 47

Camera lenses magnifying lenses ,microscope ,telescope, slide projector They are used to correct the defect of vision called hypermetropia