Light travels in straight lines called rays, and when these rays strike a surface, they obey specific laws of reflection that dictate their path.
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in our previous video we learned that we
see objects around us because of the
light reflecting from them some objects
like the Sun burning candle and the
fluorescent both emits light of their
own they are also called luminous
objects many objects around us are non
luminous status they cannot generate
their own light
however these objects reflect the light
from the luminous objects from their
surfaces and because of this reflection
we can see such objects in which
direction to the luminous objects emit
the light they emit light in all the
possible directions consider a
fluorescent bulb which is glowing it is
emitting light in all the directions let
us denote each direction with a straight
line and an arrow on it pointing in the
direction where the light is traveling
so all these arrows represent various
paths along which light is traveling
these arrows are what we call rays of
light here's how we define a ray of
light a ray of light is a straight line
path along which light travels so now we
know that light emitted by luminous
objects travel in a variety of
directions suppose rays of light from
this fluorescent bulb fall on the
surface it winged non-luminous reflects
these rays and these reflected rays
travel along a certain path consider
this plain surface suppose one of the
rays of light from the berth strikes at
this point this is called an incident
ray we know that this surface will
reflect this ray and the reflected ray
will travel in this direction why only
in this direction why not here or here
this is because rays of light obey
certain laws of reflection when they
strike any surface draw a perpendicular
to the surface at the point of incidence
this line is also called normal here are
the two laws of reflection that any
to understand the first one we first
need to know what angle of incidence and
angle of reflection are the angle of
incidence is the angle made by the
incident ray with the normal it is
denoted by I the angle of reflection is
the Angle made by the reflected ray with
the normal it is denoted by R so a first
law says that the angle of incidence is
always equal to the angle of reflection
I is equal to R here as I is equal to R
if the incident ray strikes at this
point then the reflected ray will travel
along this direction only so as to keep
the measure of are same as I if I move
the incident ray here then the reflected
ray will also move to keep the measure
of are same as I I is always equal to R
ok so this was about the first statement
what about the second statement the
second one tells us that the incident
ray reflected ray and normal all lie in
the same plane so if I draw the scenario
on the piece of paper I will get this
incident ray reflected ray and the
normal all three are in the plane of the
paper the second law tells us that they
will always be on the same plane for
example if the reflected ray is in this
direction instead of this then the
diagram will look like this the incident
ray and normal are in the plane of the
paper whereas the reflected ray is not
in this plane this violates our second
law and hence this ray will not be
reflected in that direction this is just
not possible
it can only be like this I will be equal
to R and they will lie on the same plane
I hope both the laws are clear now in
the next lesson we will see an
experiment based on this concept but you
can easily perform at home you
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