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Edu-Primes
  • 7/19/2024
Transcript
00:00hi kids today we will learn properties of light so let's start light travels
00:09very fast the speed of light in a vacuum that is an area empty of matter is around
00:173 multiplied by 10 raised to the power of 8 meters per second
00:25it takes only 8 minutes and 17 seconds for the light to travel from the Sun to
00:36the earth where the Sun is 150 million kilometers away from the earth light
00:45always travels in straight lines unless it is obstructed by something take
00:52normal torch and switch it on what do you see light always travels straight
00:59unless it's obstructed by some object here is another way to demonstrate that
01:07light travels in straight lines take four or five papers hold them one after
01:15the other at some distance like this and now flash the light on the first paper
01:23using the torch what do you find the light will hit all papers in a straight
01:30line so it shows that light travels in a straight line and light can pass through
01:41and translucent things but not opaque things stand against some source of light
01:51and as your body is opaque that is light cannot pass through it so it will cast a
01:59shadow that is light won't be able to pass through your body as it cannot pass
02:07through any opaque object here is another example where you can show that light cannot
02:15pass through opaque objects like a torch switch it on and now put your hand over it what happens
02:25to the light light is obstructed as light cannot pass through your hand which is an
02:33object all shadows are examples that light cannot pass through opaque objects next thing
02:42we can learn about light is that light travels slower in denser mediums like water and glass
02:50and light travels faster in lighter mediums like air and it is fastest in vacuum and this is why
03:02speed and direction of light changes when it enters a denser medium to thinner medium or
03:10thinner medium to denser medium because the speed of light changes light bends towards the normal
03:20when it enters the denser medium and light bends away from the normal when it enters the lighter
03:28medium next is reflection light travels in straight lines but whenever it is obstructed
03:41by some objects in its path it is reflected off and the angle of incidence is always equal to
03:51the angle of reflection and whenever light falls on an object some of the light is reflected off
03:59and some is absorbed and it depends on the object how much light is absorbed and how much will be
04:08reflected transparent objects let almost all the light pass through them translucent objects let
04:19some light pass through them and some is reflected off this is why you cannot completely see through
04:27translucent objects opaque objects does not let any light pass through so some light is reflected
04:37off and some is absorbed and surface of the object is smooth and shiny like a glass water
04:48or polished metal most of the light is reflected off and very few light is absorbed and they
04:58produce mirror like reflection which is called secular reflection and in case the surface of
05:07object is not very smooth or it is rough they absorb some light and some is reflected off
05:16and reflection is in the form of diffuse reflection light is reflected off in many
05:25directions and not in a single direction so kids today we learned a lot about the
05:33many properties of light now you may go ahead and take a quiz to learn more bye-bye