Laws of Reflection Video Lecture - Science Class 8

okay in today's video I am going to take
a few minutes to go over the law of
reflection okay here we go the law of
reflection this is our mirror the green
line here is our mirror and we have a
ray that is coming in to the mirror that
ray which is coming in to the mirror has
a very special name it is called the
incident ray that is a ray of light that
is coming into the mirror it is striking
the mirror right there and we call that
the incident ray now the next thing is
we want to draw what we were going to
call the reflected ray but whenever we
have a problem like this before we can
draw the reflected ray we have to draw a
very special line which we call the
normal line the normal line is
perpendicular to the mirror it makes a
90 degree angle with the mirror normal
means perpendicular so whenever you have
a problem like this you have the
incident ray you have the normal line
the normal line must be drawn so that it
is perpendicular to the mirror you're
going to have to get out your protractor
and draw that normal line perpendicular
to the mirror and you'll notice it is
drawn so that it meets the mirror and
the incident ray and the normal line all
meet at one point right there it's not
drawn over here somewhere or over here
somewhere it's drawn right where the
incident ray strikes the mirror then the
next thing we have is this angle right
here this is a very special angle it is
between the normal line and the incident
ray so we call it the angle of incidence
you'll notice it is measured from the
normal line to the Ray not-not-not from
the mirror to the Ray okay now we're
going to measure this angle and we're
going to draw the reflected ray so that
it reflects at the same angle relative
to the normal line so it is going to
reflect off
in this direction I think you might
understand that ahead of time somewhat
conceptually but we have to make sure
which we call that the reflected ray we
have to make sure that this angle the
angle of incidence and this angle which
we call the angle of reflection
are equal okay so now we have all the
important parts and the concepts for
that diagram we have our mirror
we are incident ray our reflected ray
our angle of incidence and an angle of
reflection and those angles are measured
always measured from the normal line to
the Ray from the normal line to the Ray
once again not from the mirror to the
Ray once again not from the mirror to
the Ray always from the normal line to
the Ray and you can see that the law of
reflection is therefore that the angle
of incidence is equal to the angle of
reflection that's all there is to it
whatever this angle is that's the same
angle you measure it with your
protractor if it's 30 degrees on this
side has to be 30 degrees on this side
if it's 70 degrees on this side has to
be 70 degrees on this side and you
should be able to see that if some
teacher was to give you the angle of
reflection then of course you could draw
the incident ray and the angle of
incidence because those would be equal
to each other eat also regardless of
which side you're coming from okay so
that's all there is to it that's the law
of reflection the two angles are equal
please measure them from the normal line
thank you very much for watching I hope
you found that helpful if you found it
helpful you can give me a thumbs up in
the comment or thumbs up below or a
comment in the comment section thank you
and we'll see you in the next video