friends today in science section we are going to learn about Reflection of light in detail. this is very important lesson for upper classes.
⚫What is light?
Light is an electromagnetic radiation which is responsible for the sensation of vision. We can also say that light gives an information about what is happening in our surrounding. With the help of light we are able to see the wonders of nature as like rainbow, sunset ,sunrise etc..
⚫What is meant by reflection of light?
The process of sending back the light rays which falls on the surface of an object is called reflection of light.
There are two type of reflections
in this ,reflection is done by the polished, shining surface.
In this type of reflection the light is reflected in one direction.
in this reflection is done by unpolished and dull surface. In this type of reflection reflected light undergo in different direction.
⚫What is mirror? what are the different type of mirrors?
Mirror is a reflecting surface. Basically a surface which is reflecting light and creating a clear image is known as mirror
There are two types of mirrors
⚫What are plane mirrors?
Mirror is formed basically coating the back surface with the thin reflecting film of aluminium or silver. To protect this layer and other coat of substance like lead oxide is also giving over it.
⚫What is silvered glass mirror?
When a ordinary glass is coated with the silver metal such mirror is called as silvered glass mirror.
⚫What are the laws of reflection of light?
According to the first law of reflection of light, the incident ray ,the reflected ray and the normal all lie in the same plane.
The angle of incidence is always equal to the angle of reflection.
⚫What are virtual and real images?
The images that are obtained on a screen is called a real image. In movie theatre the images which are formed on the screen is an example of real images
The images that are not obtained on a screen is called virtual images. For example image is formed in the mirror but the image which is formed in the mirror cannot be obtained on a screen. Therefore this is a virtual image.
⚫What are spherical mirrors?
Spherical mirror is that mirror whose reflecting surface is the part of a hollow sphere of the glass.
There are two type of sphericall mirrors
when the reflection is done by the inner surface of a spherical mirror such mirror is called as concave mirror.
when the reflection is done by the outer surface of a spherical mirror such mirror is called as convex mirror.
⚫Important terms related with a spherical mirrors
the centre of mirror surface is called pole. It is represented by p
◾Centre of curvature
Centre of curvature is the centre of sphere of which mirror is a part.
It is represented by c
◾Radius of curvature
radius of the sphere of which the mirror is a part is called radius of curvature of the mirror.
The line which is passing through the centre of curvature of the mirror and pole of the mirror is called its principal axis.
When the incident rays which are parallel to the principal axis of a concave mirror or convex mirror after reflections they are meeting at a point on the principal axes that particular point is called as principal focus or focus point of the respective mirror. It is represented by F
It is the distance between the principal focus of the mirror and the pole. It is represented by the f. It is always half of the radius of curvature of the mirror
⚫What are the rules for drawing the ray diagram?
Rule 1: first rule states that if an incident ray is parallel to the principal Axis then the reflected ray passes through the principal focus.
Rule 2: According to the second rule if an incident ray passes through the principal focus of the mirror the reflected ray is parallel to the principal axis
Rule 3: According to third rule if an incident ray passes through the centre of curvature of the mirror the reflected ray traces the same path back.
⚫What is convergence & divergence of light?
When a rays of light after reflection from spherical mirror meet at a particular point, it is called convergence of light. Example doctor use such a beam to Converse light on a tooth, near, nose
When a light ray starting from a point spread out after the reflection by spherical mirror the light is said to be divergence of light.
Example -Street lamps
⚫What are the the sign convention for reflection of light by spherical mirror.
➡️The object is always placed on the left of the mirror. All distances parallel to the principal Axis are measured from the pole of the mirror
➡️All distances are measured to the right of the pole are taken to the positive while those measured toward the left are taken to be the negative.
➡️Distance is measured vertically upward from the principal Axis are taken to be the positive.
➡️Distance is measured vertically downward from the principal Axis are taken to be negative.
➡️ The focal length of a concave mirror is negative while that of the convexbmirror is positive.
⚫What is lens mirror formula?
u…. distance of object from the pole
V…. Image distance from the pole
f…. Focal length of the mirror
⚫What are the uses of concave mirrors?
➡️ In flood light
➡️ Torch and head lamps of vehicles
➡️ Barber shop ,dental hospital
➡️ Various equipment using solar energy
⚫What are uses of convex mirror
➡️ On sides of cars
➡️ Big convex mirrors are fitted in the shops
⚫ What are diffrence between Convex mirror and Concave mirrors?
|CONVEX MIRROR||CONCAVE MIRROR|
|1||Diminished image is formed||Magnified,diminished or same sized image is formed|
|2||Focus is formed behind the mirror||Focus is formed in front of the mirror|
|3||Only virtual image is formed||Virtual as wwll as Real image is formed|
|4||Its convex(outer) surface is reflecting||Its concave(inner) surface is reflecting.|
⚫ 7th PAY COMMISSION | DA में बढ़ोतरी2022
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