L2 : Reflection of Light - Light Reflection & Refraction, Science, Class 10 Video Lecture

hello friends this video on light
reflection and refraction part 2 is
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the first phenomenon shown by light that
is known as a reflection of light so
what is the reflection of light it is
the bouncing back of a ray of light when
it strikes a boundary between different
medium through which it cannot pass let
us suppose you keep certain object
through which light cannot pass through
then what happens that suppose this is
my boundary it is some object through
which light cannot pass so what will
happen if a ray of light falls on this
boundary it has no option to pass
through with it so what will happen it
will bounce back so this phenomenon of
bouncing back of a ray of light when it
strikes a boundary between different
media because it will happen only when
it strikes something right because I am
Telling unless it strikes something it
will never bounce back it is something
like it is suppose there is a wall here
and a boy is standing here so he hits a
football so as long as the football
doesn't hit the wall it will not bounce
back right
so once the football hits this wall it
will bounce back so in order to bounce
back it is necessary that the object
hits the boundary so similarly here also
this boundary is nothing but it is a
boundary between two different medium
for example here it is air here it is
water or anything any different medium
or whatever so it should be such that
likely cannot pass through that medium
so it should it should be an opaque
medium so then what will happen it will
bounce off and this phenomenon of
bouncing back of the ray of light is
known as reflection of light so when we
think of examples of reflection of light
you can think of all these scenarios
example when you see your face in the
mirror what happens there are rays of
light for example it is suppose if there
is no light at all
inside the room right let us suppose
even the windows are closed everything
is closed will you be able to see your
face in the mirror
no that is because there is no light
present at all but if light is present
you are able to see your image on the
mirror that's because the rays of light
from your face are falling on the mirror
but since it is unable to go to the
others end it bounces back so and it
bounces back and reaches your eye and
that enables you to see your image in
the mirror now here also if you see here
this part is kept here and the image is
observed in the mirror the same thing is
happening if you look at this this is
also an actual phenomenon of reflection
here you have this water so there is a
change in medium this medium is water
and this medium is air so when the ray
of light falls on this boundary between
air and water what happens it cannot
pass through the water completely it is
not that it cannot enter water at all I
will talk about that when you talk of
refraction but the rays of light when it
falls on this boundary some of it will
bounce back and this phenomenon is known
as reflection and as a result of
reflection you see an image is formed
here you can see an inverted image of
the hill is formed on the other medium
as well right so this is known as
reflection of light now there are
certain laws which this reflection of
light follows so in fact there are two
laws which is universally followed by
this phenomenon of reflection of light
but what is it the first law see is that
the incident ray the reflected ray and
the normal on line on the same plane so
let us first talk about these three
terminologies which is a reflected ray
which is an incident ray and which is
the normal so let us suppose this is my
boundary this mirror is my boundary so
the ray of light which strikes this
mirror since this ray of light is
incident on the mirror the ray of light
which is falling on the mirror that is
known as incident today the ray of light
which bounces back from the mirror so
this ray is the ray which is formed
after reflection so this is known as a
reflected ray so this is my incident ray
this is my reflected ray and what does
Nordmann normal is an imaginary line
which is drawn perpendicular to the
plane of this boundary so if you see
this is the mirror this normal is an
imaginary line at right angles to this
surface right so the first loss is that
these three rays that is the incident
ray reflected ray and the normal all
will lie on the same plane so here you
can see that they all lie on the same
plane that is if you if you look at this
figure you can see that that they are
all lying on the same plane on the
mirror right the second loss is that the
angle of incidence is equal to the angle
of reflection now what is the angle of
incidence the angle which the incident
ray makes with the normal that is known
as the angle of incidence so this is my
angle of incidence so this angle of
incidence is between the incident ray
and the normal similarly which is the
angle of reflection it is the angle
between the reflected ray and the normal
so that means it is this angle so it
sees that this angle of incidence is
equal to the angle of reflection so that
means these two laws will always hold
true wherever reflection takes place
that is angle of incidence will always
be equal to the angle of reflection and
incidentally reflected ray and normal
always lie on the same thing thank you
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