cbse notes for class 10 science|Cbse class 10 Notes of chapter light physics download free pdf
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Mirror
Spherical mirror- of the mirror whose reflecting surface is spherical our old spiracle mirror these Mirrors are prepared by cutting a hollow glass ball.
Convex mirror- is a part of hollow sphere whose outer surface act as reflecting surface and the inner surface is polished.
This is also known as a tiger in mirror because it help to diverge the light rays this mirror always form virtual and erect image of the object
Use of concave and convex mirror
Laws of refraction
Refractive index
→All the terms of mirror and convex lenses are same except Pole in lenses it is called as optical centre . 
Power of lenses
Notes of chapter light class 10
Light- it is a form of energy that enable us to see object.
Ray of light - it is represented by a straight line having the sign of an arrow on it.
Beam of light- it is your bunch of ray of light.
Laws of reflection
1) the angle of incidence is equal to angle of reflection . Angle I = angle r.
2) the incident ray normal and reflected ray all lies on the same plane.
Mirror
Mirror glass pieces which have bright shining polish on one side( aluminium for Silver coating) . As a result of bright and Chinese repairs mirror are used for reflection of light.
Mirror →plane mirror
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Spherical mirror
Mirrors are of two type plane mirror and spherical mirror.
Plane mirror -plane mirror are flat surface mirror these are prepared by bright polishing on one side of a plane glass, silver and Aluminium are the best reflector of light.
Some properties of plane mirror
1) image formed by a plane mirror is virtual and erect.
2) size of image formed by a plane mirror is equal to the size of object.
3) the distance of the image of an object behind the mirror is equal to the distance of the object is in front of the mirror.
4) image formed by plane mirror is always laterally inverted.
Spherical mirror- of the mirror whose reflecting surface is spherical our old spiracle mirror these Mirrors are prepared by cutting a hollow glass ball.
On the basis of reflecting surface speckle Mirrors are of two types
Spherical mirror→concave
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Convex mirror
Concave mirror to use outer surface is polished and the inner surface act as reflecting surface these Mirrors are called converging mirror as they are used to convert the light ray and usually form a real image.
Convex mirror- is a part of hollow sphere whose outer surface act as reflecting surface and the inner surface is polished.
Real image - animal which is actually found by the by the light rays that converge or cross Each Other is called real image .
This image can be taken on a paper or a screen this image is always formed in front of mirror it's always inverted.
Virtual image image which is appeared to be formed behind the mirror is called virtual image when actually light rays Diverge from each other weekend project their path behind Summit we can't take on a screen or a paper it's formed always behind the mirror this type of image is always upright.
Few basic terms related to spherical Mirror
Principal axis- line joining the pole and the centre of curvature of the spherical mirror.
Pole - the geometrical centre point of the reflecting spherical surface denoted with P
Aperture- the diameter of the spherical mirror is called aperture.
Centre of curvature the centre centre of the hollow glass sphere of which the spherical mirror is a part is called as centre of curvature.
Radius of curvature the distance between pole and the centre of curvature is called radius of curvature it is denoted with R.
Focus point the point on the spherical Axis we are all parallel rays meet after reflecting in called as focus point it is denoted with f.
Focal length the distance between the pole and focus point is called focal length it is denoted with f.
F = R/2
→Concave mirror used in torch ,searchlights and vehicle headlight to get powerful parallel beam of light
→These are also used as shaving mirror to see a larger image of the face.
→Dentist use ke mirror to see large image of the teeth of thier patient.
→These mirror are also used in Solar furnace solar cooking to concentrate sunlight.
→Doctor head mirror is also a concave mirror.
Convex mirror
→Convex mirror cuffed outwardly so they provide a wider field of view and also give An erect image of the object which they are used at crowded places crossing and malls.
→ this Mirrors are commonly used in vehicle as rear view mirror.
→This mirror help the driver to see traffic behind to facilitate safe driving.
Mirror formula
In spherical mirror the the distance of the object from the pole is called object distance and denoted with u.
The distance of the image from the pole of the mirror is called image distance and denoted with v
The distance of the principal focus from the pole is called focal length denoted with f.
1/f = 1/ v + 1/ u
Magnification it is expressed as the ratio of the height of the image to height of the object it is denoted with m.
m = height of image/ height of object
Height of image = hi
Height of object= ho
m = -v/u ( m is also equal to hi / ho and -v/u)
If m >1 then the images magnified
if m= 1 then the images same size
m < 1 then the images diminished
Sign convention for reflection of by mirror
Refraction
Refraction of light is the phenomenon of bending of light from its original path on entering another medium.
Light travels in a straight line but when a light ray is passed from one medium to another which have different density it's path get deviated. This deviation is called refraction.
Refraction in daily life
Rare and denser medium
The medium whose density is lower called a rare medium.
The medium whose density is higher is called denser medium.
Refraction of light through a rectangular glass slab.
1) the incident ray, the refracted ray and the normal to interface of two transparent media at the point of the incidence, all lievthe same plane.
2) The ratio of sin of angle of incidence to the sin of angle of refraction the light of a given colour and for the given pair of media. This law is also called snells law.
Sin I/ sin r= constant.
Refractive index
Refractive Index of a medium can be define as its capacity of bending every of light it is a measure of how much the speed of light changes when it enters the medium from one medium to another medium more the binding capacity more will be the refractive index refractive index has no unit as it is simply A ratio.
Tractive Index of a medium with respect to other can be calculated by snell's law of refraction.
→ there are two type of refractive index
1) absolute refractive index
2)relative refractive index
Absolute refractive index absolute Refractive Index of a medium is defined as the ratio of the speed of light in vacuum or air to the speed of light in the medium it is denoted by n.
n = speed of light in air ( vacuum) /speed of light in medium.
n = c/v here c = speed of light ( 3×10 ^8m/s)
V = speed of light in other medium
Related refractive index the refractive index of medium 1 with respect to medium 2 is given by the ratio of speed of light in medium 2 and the speed of light in medium 1 this is usually represented by the symbol n12.
n12 = refractive index of medium 1 with respect to medium 2
n12 = speed of light in medium 2/ speed of light in medium 1
n12 = v1/v2
Factors on which the refractive index of medium depend upon
1) nature of the material of the medium 2)density of the medium
3) colour or wavelength of the medium
Spherical lenses
transparent glass material bound by two surfaces of which one or both surface are spherical form are lens.
Lens is a transparent medium bounded by a two refracting surface out of these two reflecting surface at least one surface is spherical.
There are two type of spherical lenses
1) convex lens
2) concave lens
→Convex lens whose refracting surface are spiracle such that it is thick in the middle and thin at the edge is called convex lens.
→A lens whose refracting surface are spiracle such that it is thin in the middle and thick at the edge is known as concave lens
Convex lens is covering in nature and concave lens is diverging in nature
Lens formula
Lens formula gives the relationship between object distance u,distance image distance v and the focal length f of the lens formula is expressed as
1/f= 1/v +1/u
Magnification
It is the measurement of enlargement of the image with respect to the size of the object numerically it is the ratio of image size to the size of the object it is represented by the letter m.
It can also be calculated if we have the value of U and v
m = hi / ho = v/u
Sign convention for refraction of spherical lens
Power of lenses
Power of a lens is the ability of the lens to converge or diverge the Ray of light falling on it
Power of lens is defined as the reciprocal of the focal length of the lens expressed in metre it is denoted by P.
P= 1/f ( in m) or P= 100/ f ( in CM)
Thus we can say that a length of small focal length has large power of converging or diverging a parallel beam of light on the other hand a lens of large focal length has more power of converging or diverging a parallel beam of light .
If number of lenses of power P1+ P2 +P3 .....etc are placed in contact with each other then the power of this combination of lens is given by P = P1+P2+P3....... Etc
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