The world is largely known through the senses. The sense of sight is one of the most important senses.
Through it we see mountains, rivers, trees, plants, chairs, people and so many other things around us. At
night we see the stars and moon. But how is seeing made possible? What makes things visible? You may
say that eyes see the objects. But, can you see an object in the dark? It means that eyes alone cannot see any
object. It is only when light from an object that enters our eyes we see the object. The light may have been
emitted by the object, or may have been reflected by it. A mirror changes the direction of light that falls on
it. Can you tell in which direction the light falling on a surface will be reflected?
Let us find out with the help of an activity:
Incidence Ray :The light ray which strikes any surface is called incidence Ray
Reflected ray: The ray which come back from the surface after reflection
is known as reflected ray.
Normal: A line making an angle of 90 degree with the object surface at a
point where the incidence ray strikes the mirror is known as the
normal . The line is known as normal to the reflecting surface that point
Angle of incidence(i):The angle between the normal and the incident ray is called angle of incidence.
Angle of reflection(r):Angle between the normal and reflected ray is known as angle of reflection.
• Fix a white sheet of paper on a drawing board or a table. Take a comb and close all the opening except
one in the middle. You can use a strip
of black paper for this purpose.
• Hold the comb perpendicular to the sheet of
paper. Throw light from a torch through the
opening of the comb from one side. With
slight adjustment of the torch and the comb
you will see a ray of light along the paper on
the other side of the comb.
• Keep the comb and the torch steady. Place a strip of plane mirror in the path of the light ray. What do
you observe? After striking the mirror, the ray of light is reflected in another direction.
Now check yourself:
Q1.Suppose you are in a dark room, can you see objects in the room ? Can you see objects outside the
room. Explain.
Q2.What would happen if you threw the light on
the mirror along its normal.
Q3.Label the given diagram of reflection of light:
Q4.What is reflection of light?
Q5.Can we see an object if a incident ray of light
that strikes its surface is not reflected back? Why?
Posted by Dhruv Singh
3 years, 1 month ago
