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Chapter 1:Chemical Reaction And Equations

Chapter 2:Acids, Bases and Salts

Chapter 3:Metals and Non-metals

Chapter 4:Carbon and Its Compounds

Chapter 5: Periodic Classification of Elements

Chapter 6: Life Processes

Chapter 10: Light Reflection and Refraction

Chapter 11:Human Eye and Colourful World

Chapter 12:Electricity

Chapter 13:Magnetic Effects of Electric Current

Chapter 14:Sources of Energy

Chapter 15:Our Environment

Chapter 16:Sustainable Management of Natural Resources

Light Reflection and Refraction class 10 notes chapter 10

Light is a form of energy . Light help us to see thing around . we can see non luminous object because they reflect light into our eyes

Reflection Of Light:

The bouncing back the light rays which fall on the surface of an object is called reflection of light
The best metal for reflector of ligth is Silver
iii) A bundle of light ray is called beam of light

Incident ray: The light ray which fall on the surface is known as incident ray

Reflected ray The light ray which bounce back from the surface is know as reflected rays

Normal An imaginary line produce when light ray which fall on the surface is known as normal

Angle of incident rayAn angle produce by incident ray with normal at the point of incidence is know as angle of incident

Angle of reflectionAn angle produce by reflected ray with normal at the point of incidence is know as angle Reflected

Laws of Reflection

i)First Laws of Reflection The incident ray, the normal to the mirror at the point of incidence and the reflected ray, all lie in the same plane.
ii)Second Laws of Reflection The angle of incidence is equal to the angle of reflection




Note: Law of reflection is apply all kind of mirror (plane ,sperical mirror)

Regular reflection When parallel rays remain parallel after reflection in one direction


Diffuse reflectionA parallel ray of incident light is reflected in different direction


Real image A images which can be obtain on a screan are know as real image

Virtual image A images which can not be obtain on a screan are know as virtual image

Image formation by a plane mirror




i)The image formed by a plane mirror is always virtual and erect.
ii)Object and image are equidistant from the mirror
iii)The image is laterally inverted.

SPHERICAL MIRRORS:

The mirrors, whose reflecting surfaces are spherical, are called spherical mirrors. The spherical mirrors are the two type :
i) Concave mirror

Concave mirrorA spherical mirror, whose reflecting surface is curved inwards, that is, faces towards the centre of the sphere, is called a concave mirror.


Convex mirrorA spherical mirror whose reflecting surface is curved outwards, is called a convex mirror



Pole(P)The centre of the reflecting surface of a spherical mirror is a point called the pole.

Centre of curvature(C)The reflecting surface of a spherical mirror has a centre. This point is called the centre of curvature of the spherical mirror.

ApertureThe diameter of the reflecting surface of spherical mirror is called its aperture.

Radius of curvatureThe radius of the sphere of which the reflecting surface of a spherical mirror forms a part, is called the radius of curvature of the mirror

Principal Focus A point on the principlal axis of a spherical mirror where the rays of light parallel to the principal axis meet or appear to meat after the reflection from the mirror

Focal Lenght The distance between principal focus and pole . it is denoted by f

Note: foacl length is equal to half of its radius of curvature
R = 2f

Image Formation by Spherical Mirrors

Representation of Images Formed by Spherical Mirrors Using Ray Diagrams

i)A ray parallel to the principal axis, after reflection, will pass through the principal focus

ii)A ray passing through the principal focus becomes parellel to principal axis

iii)A ray passing through the centre of curvature reflect back along same direction

iv)A ray incident to the pole is reflect back making same angle with principal axis

Image formation by Concave Mirrors


Uses of concave mirrors
i)Concave mirrors are commonly used in torches, search-lights and vehicles headlights to get powerful parallel beams of light
ii) Concave mirrors are often used as shaving mirrors to see a larger image of the face
iii)Large concave mirrors are used to concentrate sunlight to produce heat in solar furnaces
iv). The dentists use concave mirrors to see large images of the teeth of patients

Image formation by a Convex Mirror



Uses of convex mirrors
i)Convex mirrors are commonly used as rear-view (wing) mirrors in vehicles.
ii) Big convex mirror are used as shop and railway station security mirror

Sign Convention for Reflection by Spherical Mirrors
According to Cartesian Sign Convention

(i)Sign of object distance always taken as negetive value
(ii) All distances parallel to the principal axis are measured from the pole of the mirror.
(iii) All the distances measured to the right of the origin are taken as positive while those measured to the left of the origin are taken as negative.
(iv) Distances measured perpendicular to and above the principal axis (along + y-axis) are taken as positive.
(v) Distances measured perpendicular to and below the principal axis (along –y-axis) are taken as negative


Mirror Formula:

1 / f
=
1 / u
+
1 / u

where , u =Object distance
v =Image distance
f= focal length
Note: value of object always taken as negetive

Magnification the ratio of the height of the image to the height of the object are known as magnification

Magnification =
height of the image / height of the object

m=
hi / ho

or

The magnification m is also equal to the ratio object distance (u) and image distance (v). Magnification = -
image distance / object distance

m = -
v / u

Note: Negative sign of mgnification indicates that the image is real. and positive indicate image is virtual

REFRACTION OF LIGHT

The change in direction of light when it pass from one medium to another medium is known as refraction of light



In case of refraction, The angle of incidence is not equal to angle of refraction
When light pass from rarer medium to a denser medium its bend toward the normal


When light pass from denser medium to a rarer medium its bend away the normal


Laws of refraction of light
(i) The incident ray, the refracted ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane.
(ii) 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.

sin i / sin r
= constant
This constant value is called the refractive index of the second medium with respect to the first.

The Refractive IndexThe ratio of the speed of light in medium 1 and the speed of light in medium 2.

n21=
Speed of light in medium 1 / Speed of light in medium 2
      
V 1 / V2

Refraction by Spherical Lenses

Image Formation by Lenses

i)A ray parallel to the principal axis, after refraction, will pass through the principal focus


ii)A ray passing through the principal focus becomes parellel to principal axis


iii)A ray of light passing through the optical centre of a lens will emerge without any deviation


Concave



Image Formation in Lenses Using Ray Diagrams



Convex


Lens Formula

1 / f
=
1 / v
-
1 / u

Magnification

Magnification =
height of the image / height of the object

m=
hi / ho

or

The magnification m is also equal to the ratio object distance (u) and image distance (v). Magnification =
image distance / object distance

m =
v / u

Power of a Lens (P)
The ability of a lens to converge or diverge light rays depends on its focal length

P=
1 / f

SI unit of powerThe SI unit of power of a lens is ‘dioptre’. It is denoted by the letter D.

The power of a convex lens is positive and that of a concave lens is negative