Light

Front 1

How fast does light travel

Back 1

Speed of light in a vacuum is 3×10⁸m/s

Front 2

Long does it take for light from the sun to reach the earth

Back 2

8 minutes 20 seconds

Front 3

Rectilinear propagation of light

Back 3

light travels along a straight line. Its path changes only when something comes in its path or when there is a change of medium. This is called rectilinear propagation of light.

Front 4

Reflecting surfaces/reflector

Back 4

A surface on which light falls and reflects back into the same medium is known as a reflecting surface

Front 5

Laws of reflection

Back 5

The angle of incidence is always equal to the angle of reflection

the incident ray the reflected ray and the normal all lie at the point of incidence on the same plane

Front 6

Reflection

Back 6

the process of a Ray of light striking a reflecting surface or reflector and bouncing back into the same medium is known as reflection of light

Front 7

Real image

Back 7

The image formed when the reflected rays of light meet at a point. It can be obtained on a screen and is always inverted.

Front 8

Virtual Image

Back 8

if the reflected rays of light do not actually meet at a point but appear to meet when produced backwards the image formed is called a virtual image. It cannot be obtained on a screen and is always erect.

Front 9

Incident ray

Back 9

the ray of light which strikes any surface is called incident ray

Front 10

Point of incidence

Back 10

The the point at which the incident ray falls on the reflecting surface. The incident ray reflected ray and normal are all on this point.

Front 11

Normal

Back 11

It is the line drawn perpendicular to the reflecting surface at the point of incidence

Front 12

Angle of incidence

Back 12

The angle made by the incident ray with the normal at the point of incidence. Is represented by i

Front 13

Angle of reflection

Back 13

Angle made by reflected ray with the normal at the point of incidence. It is represented by r.

Front 14

LET

Back 14

light Emitting diode

Front 15

Luminous bodies

Back 15

Bodies which give light on their own are called luminous bodies

Front 16

Non luminous bodies

Back 16

Bodies which do not give out light on their own but I am made visible due to the reflection of light are called non luminous bodies

Front 17

Characteristics of an image formed by a plane mirror

Back 17

Image formed by a plane mirror is virtual and erect

The size of the image is equal to the size of the object

The distance of the image from the mirror behind it is equal to the distance of the object from the mirror infront of it

The image undergoes lateral inversion that isthe right side of the object appears to be the left side and vice versa

Front 18

Concave mirror

Back 18

A mirror part of a hollow sphere whose outer surface is silver and inner surface acts as the reflecting surface

Front 19

Convex mirror

Back 19

Part of a hollow sphere whose outer surface acts as a reflecting surface and the inner surface is silvered

Front 20

Centre of curvature

Back 20

the centre of a hollow sphere of which the curved or spherical mirror forms a part is called centre of curvature. It is denoted by C.

Front 21

Radius of curvature

Back 21

The radius of a hollow sphere of which the serical mirror forms a part is called radius of curvature. Denoted by R

Front 22

Pole

Back 22

The midpoint of a spherical mirror is called its pole. It is denoted by P.

Front 23

Aperture

Back 23

the diameter of the part of a spherical mirror exposed to the incident light is called the aperture of the spherical mirror

Front 24

Principal axis

Back 24

A line joining the centre of curvature and pole Avis perikal mirror and extended on either side is called principal axis

Front 25

Principal focus

Back 25

a point on the principal axis of a spherical mirror where the rays of light parallel to the principal Axis meet or a appear to meet after reflection from the spherical mirror is called principal focus. It is denoted by f. It is real for a concave mirror and virtual for convex mirror.

Front 26

Focal plane

Back 26

A plane normal or perpendicular to the principal axis and passing through the principal focus of a spherical mirror.

Front 27

Focal length

Back 27

The distance between the pole and principal focus of a spherical mirror is cal focal length it is denoted by f

Front 28

Uses of concave mirrors

Back 28

Torches, search lights and vehicle headlights to get powerful parallel beams of light

Used as shaving mirrors or by dentist s to see larger images of the face or images of the teeth of patients

Large conch give me this I used to concentrate sunlight to produce heat in solar furnaces

Front 29

Uses of convex mirrors

Back 29

Rear view mirrors in vehicles enabling the driver to see traffic behind them to facilitated safe driving

Preferred because they always given erect the diminish image and have a wider field of view as they are curved outwards.

Front 30

U

Back 30

In a spherical mirror the distance of the object from its pole is called the object distance (u).

Front 31

V

Back 31

In a spherical mirror the distance of the image from the pole of the mirror is called the image distance (v)

Front 32

Magnification produced by a spherical mirror

Back 32

magnification produced by a spherical mirror gives the relative extent to which the image of an object is magnified with respect to the object size. It is expressed as the ratio of the height of the image to the height of the object. It is usually represented by the letter m.

Front 33

Refraction of light

Back 33

Refraction is the phenomena by which the direction of propagation of light changes when it passes from one transparent medium to another of different optical density. This is because the speed of light is different in different media.

Front 34

Optically rarer medium

Back 34

A medium in which the speed of light it is comparatively more

Front 35

Optically denser medium

Back 35

A medium in which the speed of light is comparatively less

Front 36

Laws of refraction

Back 36

The incident ray, refracted ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane

The ratio of sine of angle of incidence to the Sine of angle of refraction is a constant for the light of a given colour and for the given pair of media. This law is also known as snell's law of refraction

Front 37

Why is the emergent ray parallel to the incident ray

Back 37

The extent of refraction of light at the opposite parallel faces is equal and opposite.

Front 38

Refractive index

Back 38

The amount of change in the speed of light in a medium depends upon a property of the medium known as refractive index.

Front 39

Absolute refractive index

Back 39

Absolute refractive index of a medium is defined as the ratio of the speed of light in vacuum to the speed of light in the medium. It is denoted by n

Front 40

Relative refractive index

Back 40

Relative refractive index of medium 2 with respect to medium 1 is defined as the ratio of absolute refractive index of medium 2 to the absolute refractive index of medium 1

Front 41

Refractive index of air

Back 41

1.0003

Front 42

Refractive index of ice

Back 42

1.31

Front 43

Refractive index of water

Back 43

1.33

Front 44

Refractive index of alcohol

Back 44

1.36

Front 45

Refractive index of kerosene

Back 45

1.44

Front 46

Refractive index of fused quartz

Back 46

1.46

Front 47

Refractive index of turpentine oil

Back 47

1.47

Front 48

Refractive index of benzene

Back 48

1.5

Front 49

Refractive index of crown glass

Back 49

1.52

Front 50

Refractive index of Canada balsam

Back 50

1.53

Front 51

Refractive index of rock salt

Back 51

1.54

Front 52

Refractive index of carbon disulphide

Back 52

1.63

Front 53

Refractive index of dense flint glass

Back 53

1.65

Front 54

Refractive index of Ruby

Back 54

1. 71

Front 55

Refractive index of sapphire

Back 55

1.77

Front 56

Refractive index of diamond

Back 56

2.42

Front 57

Optical density

Back 57

Optical density of a medium determines the ability of the medium to refract light. Optical density of the medium is directly proportional to the refractive index of the medium.

Front 58

Mass density

Back 58

Mass per unit volume of a substance

Front 59

Factors on which refractive index of a medium depends

Back 59

Nature of the material of the medium

density of the medium

colour or wavelength of the light

Front 60

Lateral shift or displacement

Back 60

The perpendicular distance between the direction of the original path of incident ray and the direction of emergent ray coming out of a glass slab

Front 61

Factors on which lateral shift depends

Back 61

Lateral shift there is directly proportional to the thickness of the slab

Lateral shift varies directly proportional to the incident angle

Lateral shift varies directly proportional to the refractive index of a glass slab

Lateral shift varies inversely proportional to the wavelength of incident light

Front 62

Magnification produced by a lens

Back 62

The ratio of the height of an image to the height of the object is known as the magnification produced by the lens

Front 63

Power of a lens

Back 63

Power of a lens is defined as the reciprocal of the focal length of the lens. SI unit is dioptre D

Front 64

1 dioptre

Back 64

Power of a lens is 1 diopter if its focal length is 1 metre

Front 65

Equivalent lens

Back 65

When two lenses and in contact the combination behaves as a single lens of focal length F and is called equivalent length

Front 66

Applications of lenses

Back 66

A convex lens is used to form the image of an object on the film of a camera

A convex lens is used in astronomical telescope to see the heavenly objects

A convex lens of small focal length is used in microscope to study biological specimens

A convex lens is used to correct hypermetropia

A concave lens is used to correct myopia