Light - Properties Video Lecture - Science Class 8

hello kids let us understand more about
light as the light travels from the
source to a point can the light pass
through various objects which come in
its way before this let us analyze what
you do when you play hide-and-seek with
your friends all the kids love the game
of hide-and-seek
what are places would you like to hide
so that you are not seen by others yes
you might hide behind the wall or the
trunk of a huge tree would you like to
hide behind a glass window not at all
because your friends can see through and
spot you that means you cannot see
through all the materials correct like
in the case of the wall or the tree
trunk so we cannot see through certain
materials and we can see through certain
materials is there something in between
yes let's take the case of a colored
glass or dirty water we can see through
them but not clearly those substances or
materials through which we can see are
called transparent materials clear glass
clear water air and some plastics are
the example of transparent materials we
cannot see clearly through a deeply
colored glass waxed paper dirty water
and some plastic that's why they are
called as translucent materials those
substances or materials through which
things cannot be seen at all are called
opaque materials now you must be
thinking why is it so that we can see
through a glass but not through a brick
wall why can we see through transparent
but not through opaque objects
we were initially talking about light so
you might also think what has light to
do with all these things
well light comes into picture when we
talk about the transparency or opacity
of things you know a glass allows all
the light to pass through it and hence
we can see through it clearly now you
know why we can see through all the
transparent materials translucent
materials like a colored or frosted
glass transmits only some amount of
light that is they allow only some
amount of light to pass through them so
we can see through them partially not
clearly coming to opaque materials like
a brick wall and even we humans
completely block the light none of the
light passes through the majority of
light is sent back by the object hence
we cannot see through the opaque
material so now we conclude that a given
object or material could be transparent
translucent or opaque depending on
whether it allows light to pass through
it completely partially or not at all we
see the various non luminous objects
like a table or a pen when the light
from a luminous object such as Sun or
torch falls on these and then travels
towards our eyes have you ever thought
what part does the light follow is it a
straight or curved or zigzag path let us
find it out light a candle and fix it on
the table at one end of the room take a
piece of pipe or a long rubber tube now
look at the candle through the long pipe
or the rubber tube is the candle visible
now yes it is
now bend the pipe a little while you are
looking at the candle is the candle
visible now no try to turn the pipe a
little tool right or left still the
candle won't be visible from the pipe so
what do we conclude from this this
suggests that the light travels along a
straight line isn't it light in any
medium travels along a straight line
from the source to any point just think
what would happen if light didn't travel
in a straight line then the object you
see will not be actually where you think
it is it will become difficult to locate
the object right but we don't face any
such problem because light travels in a
straight line
to summarize different types of material
can pass different amount of light
through them the transparent object
allows all the light to pass through it
and hence we can see clearly through it
on the other hand the opaque object does
not allow any light to pass through it
and hence we cannot see through an
opaque object in between these two lies
the translucent object that doesn't
allow all but allow only some amount of
light to pass through it and so we can
see through the translucent object
partially but not clearly and lastly the
light travels in a straight line from a
source to any point that's all for today
kids enjoy your day bye bye kids