"Experiment - Light travels in a Straight Line Video Lecture - Class 12

never try to attend an experiment
without an adult supervision me often
reading text flows that light travels in
a straight line do you believe that have
you ever observed the beam of light
entering inside a dark room through a
tiny hole in the window
what do you see do you see light
traveling in straight line hello friends
today we will perform a very simple
experiment to prove that light indeed
travels in a straight line all that you
would need to start the experiment are
three old CDs so the CD should be old
because during the experiment they might
get scratched thread a candle and six
clips these waves we normally use to dry
clothes so first of all we will have to
make stand for these CDs so for that we
will make use of these clips so hold to
the CD upright and then fix the clip
please make sure that the CD remains
upright that is it should be
perpendicular to the plane of the table
so this is ready in a similar way we
will do it for the other two CDs so now
all the three CD stands are ready so
what we want to do now is we want to
align these three in a straight line we
have to align them in such a way that
the holes of the three CDs lying in a
straight line so how do we ensure that
they are in a straight line so for that
purpose we will use a thread so we take
this thread and we tie it straight on
the table so you can make use of
sellotape to fix it at both ends so you
see now you have a straight line so now
we will place the CDs one after another
so now when you place them on the thread
then you know that they are exactly in
straight line now you take the candle
and place it at one end again place the
candle also on the thread
so now make sure that the tip of the
candle and the holes of the CDs all of
these lie in a straight line so for that
you will have to ensure that the height
of the candle and the height of the hole
of each of the CDs they are the same now
try to observe the flame of the candle
from the other side so your line of
sight should be same as this line the
holes on the CDs and you are able to see
the flame right now yes okay now why do
you see this flame that's because light
travels through these holes and reaches
your eye now let's see what happens if
we displace the middle CD slightly the
moment we displace it a bit what happens
are you still able to see the flame no
why did that happen that's because the
light came here and it got blocked here
because we have displaced the CD the
hole is not it so the light is not able
to come any further and you are not able
to see it now I'd like the ability to
take curved turns in that case light
could have actually taken this turn and
then it could have come through this
hole and you could have seen it but
since light travels in a straight line
therefore we did not see the flame so
this experiment very clearly proves that
light always travels in a straight line
few important points to be noted while
performing this experiment CDs must be
perpendicular to the plane of the table
old CD should be used holes of CDs and
candle flame should be in a straight
line presence of the thread ensures that
the CDs lie in a straight line line of
sight should be along the line of candle
flames and the holes of the CDs last but
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