light, reflection and refraction class 10 1st blog

Notes Prepared by 

Ashaq Hussain Bhat

Teacher school Education

department U T 

Jammu and Kashmir

Light , Reflection and Refraction 

Blog 1st

Introduction 

all of us are familiar with light at night, when we switch on bulb everything in the room becomes visible, nothing is seen when the bulb is off. during the day we are able to see the world around us due to the light  from the Sun, in fact sunlight falling on the object is reflected or scattered by them into our eyes and we are able to observe them, we may therefore consider light as a form of energy which produces in us the sensation of sight thus light is an in dispensable tool to explore the colourful beauty of nature .

yet another application of light is is in communication optical fibres have been designer to transmit light signal over long distances without loss of intensity a of Optical Fibre can carry as many as 3000 telephone simultaneously

Light has a dual character. It is either emitted or absorbed as a particle, but it propagates as a wave let's learn more about light

Some important terms related with light

 Source :-a source of light is an object from which light is given out .some sources of light are natural and many other are man made eg, Earth, Sun is the most important natural source of light , electric lamp and oil lamp a candle are some of the sources of light 

the sources of light are two types

1  Self-luminous :-self Luminous source is that which possesses light of its own for example the sun star electric lamp candle  etc 

2  Non luminous source is that which does not possess light of its own it receives light from an external source and scatter it to the surroundings for example the moon, a book, table and chair etc 

Medium 

A medium is a substance through which light propagates or tries to do so there are three types of media of light

1. Transparent  

2 .Translucent

3.Opaque

1 Transparent :-it is a media through which light propagates easily for example air, water, glass etc at 

2 Translucent :-it is a medium through which light propagates partially for example paper glass etc

 3 Opaque:- it is a medium through which light cannot propagate for example wood ,metal ,etc 

Ray:- A Ray of light  is the straight line path along which light travels the arrow head of it  represents its direction of propagation ,a number of rays combined together form a beam of light and  narrow beam is called Pencil of light

Pencil of light may be of three kinds one 

• Convergent pencil
•  Divergent pencil 
• Parallel pencil 

Reflection of light 

Reflection of light is the phenomenon of bouncing back of light in the same medium on striking with the surface of any object reflection, is of two types regular reflection and irregular reflection 

1 Regular reflection when the reflecting surface is smooth and well polished The parallel rays Falling On It are reflected parallel to one another as shown in 

figure 

the reflected light  goes into one particular direction This is regular reflection   mirror, silver metal, is one of the best reflector of light

2 Regular reflection when the reflected surface is rough the  parallel rays Falling On It are reflected in different direction  as shown in figure such a reflection is known as diffused reflection or irregular reflection

Laws of reflection of light

 there are two laws of reflection of light 

First law:-according to this law the incident ray the reflected ray and normal at the point of incidence all lie in the same plane . 

Second law  according to this law the angle of reflection r    is always equal to the angle of incidence (i) the laws of reflection is applicable to all types of reflecting surfaces including Spherical surfaces we must remember one thing also a Ray of light incident normally on the mirror retraces its path on reflection as shown in fig

Characteristics of images formed by plane mirror 

following are the important characteristics of images formed by plane mirror 

1:-the image of a real object is always virtual such an image cannot be taken on a screen

2:- the image formed in a plane mirror is always erect up side of the image is upside of the object and vice versa 

3:-the size of image in a plane mirror is always the same as the size of the object 

4:- the image formed in a plane mirror is as far behind the mirror as the object is in the front of the mirror 

5:-the image formed in a plane mirror is laterally inverted that is left side of the object becomes right side of the image and vice versa

Continue on  2nd blog . .......