Dispersion of Light
Summary
TLDRIn this exciting video, we explore the fascinating world of light dispersion and the spectrum using a color-changing magic bulb. Through engaging experiments with colored lights and blocks, we demonstrate how different colors of light reflect and absorb, revealing the principles of light behavior. We delve into the dispersion of white light into its constituent colors using a prism, explain how rainbows form through dispersion and total internal reflection, and conclude with key concepts and interactive questions. Join us for a colorful journey into the science of light!
Takeaways
- 💡 The video introduces an experiment using a 'magic' lightbulb that can change colors through an app on a phone.
- 🌈 It demonstrates light dispersion by showing how objects appear under different colored lights, explaining that objects reflect light that matches their color and absorb others.
- 🔴 The red block appears red under red light but black under green and blue light, illustrating the concept of light absorption and reflection.
- 🟢 Similarly, the green and blue blocks are shown to reflect their respective colors and absorb others, appearing black under non-matching light.
- 💡 The conclusion is that an object reflects light that matches its color and absorbs all other colors, which is why they appear differently under various lights.
- 🌟 White light is revealed to contain millions of colors, not just the simplified seven colors of the rainbow (VIBGYOR).
- 🎨 The script explains that different colors of light have different frequencies, similar to how different sounds have different frequencies.
- 📐 The dispersion of white light is shown through the use of a glass prism, which splits white light into its constituent colors, forming a spectrum.
- 🌈 The natural phenomenon of a rainbow is discussed as an example of light dispersion, formed by raindrops acting as tiny prisms.
- 🔍 The process of refraction and total internal reflection within a raindrop is explained to describe how a rainbow's colors are formed.
- 🔄 The video suggests that placing an inverted second prism after the first can recombine the dispersed colors back into white light.
Q & A
What is the main purpose of the video?
-The main purpose of the video is to educate viewers on the concept of light dispersion, the colors of light, and the spectrum, using an interactive experiment with a magic lightbulb and colored blocks.
How does the magic lightbulb work?
-The magic lightbulb can change colors using an app on the presenter's phone, allowing the viewer to see how different colors of light affect the appearance of objects.
Why do the red, green, and blue blocks appear black under a color of light that doesn't match their own?
-Objects appear black under a color of light that doesn't match their own because they absorb that color of light and do not reflect it back to the viewer.
What is the conclusion of the experiment with the colored blocks and the magic lightbulb?
-The conclusion is that an object reflects light that matches its color and absorbs all other colors of light, which is why objects appear different colors under different colored lights.
What does the script tell us about white light?
-White light is not actually white; it contains millions of colors, including the three primary colors red, green, and blue, which can be seen when white light is dispersed.
How does the frequency of light waves relate to the colors of light?
-Different colors of light have different frequencies. For example, red light has a different frequency from green light, and this variation in frequency results in the different colors we see.
What is the phenomenon called when white light is split into its constituent colors?
-The phenomenon is called dispersion of light, and the resulting band of colors is known as the spectrum.
Why do we see a rainbow in the sky but not always?
-A rainbow is formed when sunlight is dispersed by raindrops, which act like tiny prisms. It is rare because it requires both rain and sunshine at the same time, and it only lasts for a short period.
What is the role of refraction in the dispersion of light through a prism?
-Refraction is the bending of light as it passes from one medium to another, such as from air to glass. Different colors of light bend at different angles due to their different speeds in the medium, leading to the dispersion of white light into its constituent colors.
Why do we see a rainbow near a waterfall, and how is it formed?
-A rainbow is always visible near a waterfall because the constant presence of water droplets provides the necessary conditions for dispersion of sunlight. The raindrops act as prisms, splitting white light into its constituent colors through refraction and total internal reflection.
What happens when a second inverted prism is placed after the first one in the experiment?
-When a second inverted prism is placed after the first one, the dispersed colors of light are recombined back into white light, demonstrating that white light contains the seven colors of the spectrum.
Outlines
🌈 Exploring Light Colors and Spectrum
This paragraph introduces an interactive experiment on light dispersion and the spectrum using a 'magic' lightbulb that changes colors via a smartphone app. The presenter demonstrates how different colored blocks appear under red, green, and blue light, explaining the principle that objects reflect light that matches their color and absorb other colors. The concept of white light containing a spectrum of colors is introduced, emphasizing that it's composed of millions of colors, not just the simplified seven colors of the rainbow.
🔍 Understanding Light Frequency and Dispersion
The second paragraph delves into the science behind light's different colors, comparing light waves to sound waves and their frequencies. It explains how a glass prism can disperse white light into its constituent colors, forming a spectrum. The paragraph provides examples of natural and man-made dispersion, such as rainbows and the colorful patterns seen on CDs. The explanation of refraction and the varying speeds of light waves in different media, like glass, is key to understanding how a prism splits and then recombines light into a spectrum.
🌈 The Science of Rainbows and Light Refraction
The final paragraph discusses the natural phenomenon of rainbows, explaining the conditions necessary for their formation and how they are a common sight near waterfalls like Niagara Falls. It describes the process of light entering a raindrop, being dispersed into seven colors, undergoing total internal reflection, and then refracting out to form a rainbow. The paragraph concludes with an invitation for viewers to engage with the content by answering top three questions related to the topic and interacting in the comments section of the video.
Mindmap
Keywords
💡Light Dispersion
💡Spectrum
💡Color Absorption
💡Refraction
💡Frequency
💡White Light
💡Rainbow
💡Total Internal Reflection
💡Critical Angle
💡Prism
Highlights
Introduction to the experiment with a magic bulb that changes colors using an app.
Demonstration of how different colored blocks appear under red, green, and blue light.
Explanation of why objects appear black under non-matching light due to absorption.
Concept that objects reflect light matching their color and absorb others.
Example of a red block reflecting red light and absorbing others, appearing black under non-red light.
Observation that white light contains red, green, and blue, and millions of other colors.
Discussion on the nature of light and sound as waves with different frequencies.
Experiment showing the dispersion of white light into a spectrum using a prism.
Spectrum of light contains millions of colors, simplified to seven for demonstration.
Examples of everyday dispersion of light, such as rainbows and CD reflections.
Explanation of how a prism refracts light and causes dispersion due to different speeds of colors in glass.
Experiment showing recombination of colors back to white light with two prisms.
Natural occurrence of rainbows and the conditions required for their formation.
Detailed process of how raindrops act as prisms to create a rainbow.
Importance of colorful light for visual diversity compared to black-and-white.
Invitation to engage with the content through comments and social media.
Conclusion and call to action for subscribing and following the channel.
Transcripts
hi friends are you ready to learn about
colors of light dispersion and spectrum
in an exciting way I have this lightbulb
here with me it looks like a simple
white bulb but it's actually a magic
bulb because I can change the color of
this bulb using an app on my phone here
let me show you how so we have so many
colors to choose from for example red
light pink blue green light yellow
wasn't that cool now I'm going to turn
off all the lights in the room and we
are going to use only this bulb and we
are going to look at these three blocks
under different colors of light red
light green light and blue light and
let's see what these blocks look like on
the colored light and as usual we'll
finish off with our top three questions
on this topic so are you ready for our
exciting experiment lights off please I
am now going to turn on our magic bulb
first as you can see the bulb is giving
off white light we have three blocks
here red green and blue now I'm going to
change the color of the bulb to red Wow
can you see the red block here but we
can't recognize the color of the other
two blocks they appear blackish this is
in fact the green block and this is the
blue block now why is this happening
because there's only red light here and
the red block is able to reflect the red
light so it's visible and appears red in
color but the green block absorbs all
the red light and has nope like to
reflect so it appears black and same is
the case with the blue block it absorbs
the red light and hence appears blackish
in color now I'm going to change the
color of the bulb to green under green
light can you see that the green glow
is visible but the red block and the
blue block appear black-ish in color
because the green block is reflecting
all the green light but the red block
and the blue block absorb the green
light hence they appear blackish now I'm
going to change the color of the bulb to
blue now what do we have here under blue
light can you see that the blue block is
now visible but the green and red block
appear dark of black in color because
the blue block is reflecting all of the
blue light but the green and red block
are absorbing the blue light and hence
they appear black in color so what's our
conclusion from the experiment an object
reflects light that matches the color of
the object and it absorbs all other
colors of light let's take an example if
we consider this red block here it's
reflecting red light that's why it
appears red to us but it's absorbing all
the other colors of light now when this
red block was placed under different
colored light what did it look like
so under red color it looked red in
color but when placed in blue and green
light it looked black because it was
absorbing the green and blue light and
it was not able to reflect any light
because it can only reflect red light
that's why it appeared black
similarly the green block was visible
under green light but appeared blackish
under red and blue light and same is the
case for the blue block so clearly we
can see that these objects are
reflecting light of their color but they
are absorbing all the other colors when
we look at these three blocks under
white light whether it's coming from
this bulb or from the lights in this
room we can see all the three colors red
green and blue the red block is
reflecting red light the cream block
reflects green light and the blue block
reflects blue light so what does this
tell us about white
light white light is actually not white
it at least contains these three colors
red green and blue but do you know how
many colors there are actually in white
light that's right the correct answer is
white light contains millions and
millions of colors you may have heard of
the seven rainbow colors or the VIP pure
colors but that's just a simplification
white light is made up of millions and
millions of colors now an interesting
question is why does light have
different colors so what is the
difference between red light green light
or blue light
let's compare light with sound light and
sound are both energies they are waves
so when I play music in this keyboard
why do these sound sound different
what's the difference between these
sounds that's right these different
sounds have different frequency
similarly different colors of light are
light waves having different frequency
so the frequency of red light is
different from green light and that's
different from blue light and all these
light waves of different frequencies
make up white light now can we separate
the colors of white light absolutely
let's take a look how when you shine
white light on a glass prism as you can
see the glass prism splits the white
light into its constituent colors and
this splitting of white light into its
constituent colors is called dispersion
of light and the band of colors obtained
by this dispersion of light is called
spectrum as we discussed the spectrum
band contains millions and millions of
colors but here we've just shown the
seven rainbow colors the Vibgyor colours
violet indigo blue green yellow orange
and red just for simplicity but actually
there are millions and millions of
colors there
now can you think of examples where
you've seen a spectrum where you've seen
the dispersion of light one simple
example is the beautiful rainbow where
you see the white sunlight splitting
into the different colors and another
everyday life example is if you look at
the back of a CD or DVD have you seen
the different colors it looks almost
like a rainbow
that's your spectrum and it's happening
due to dispersion of light as we learnt
white light is made of seven different
colors violet indigo blue green yellow
orange and red this band of seven colors
is known as spectrum and the splitting
of white light into its constituent
colors is known as dispersion of light
now let's understand how our simple
glass prism is able to split the white
light into different colors for this we
need the concept of refraction remember
refraction means bending of light so
let's start off by shining light of a
single color known as monochromatic
light let's say red light here onto our
glass prism and as you can see the light
is traveling from air to glass so
there's a bending or refraction there
and once again there's a bending when
light comes out of the prism so from
glass to air and as you can see the red
light is bending towards the base of the
prism here now let's replace the red
light with white light again for
simplicity we'll consider that white
light is made up of the seven web gear
colors now one important point to
remember is that different colors of
light have the same speed in air
approximately 3 into 10 to the power 8
meter per second so all our seven colors
are traveling at the same speed in air
but the moment they hit the glass prism
the speed of the different colors
changes in the glass prism red has the
maximum speed and violet has the
minimum speed so because of the change
in speed of the different colors they
Bend at different angles in the glass
prism so as you can see they split there
and then there is another refraction
when these different colors are coming
out from the glass to the air so this is
how the glass prism is able to split the
white light into its constituent colors
so the important point to remember is
all the colors have the same speed in
air otherwise we'll be seeing a rainbow
right here in the air but in glass or in
any other medium different colors have
different speeds and that's how they
split up as we saw a glass prism splits
the white light into seven different
colors now what do you think is going to
happen if he place a second prism but
it's inverted after the first one that's
right we are going to get back white
light again so these two prisms are
showing that white light contains seven
colors
the first one is splitting the white
light into seven colors and the second
prism recombines the seven different
colors back to white light let's place
the concepts we have learned so far on
our concept boat now let's talk about
nature's beautiful spectrum the rainbow
I'm sure you've seen a rainbow but it's
pretty rare right because you need both
rainfall and sunshine happening at the
same time and it only lasts a few
seconds or a few minutes but can you
think of some places where you'll always
see a natural rainbow one thing that
comes to my mind is near a waterfall
I've been to the Niagara Falls and there
you always see a rainbow it never
disappears and people are clicking
pictures around that rainbow let's
discuss how a rainfall rainbow is formed
to see the rainbow you need the Sun
behind you and you need to be looking
towards the rain
the raindrops are acting like tiny tiny
prisms and they are splitting the white
light of the Sun into the seven
different colors forming our rainbow but
it's not just dispersion of light
involved there's some other stuff going
on
let's take up closer look let's consider
one raindrop for simplicity when the
white light from the Sun enters the
raindrop just like the prism it splits
into seven colors because light is
entering from air to water in the
raindrop and we know that different
colors of light will have different
speeds in water so there's dispersion
there now rather than all the colors of
the light leaving the raindrop an
interesting thing happens which is known
as total internal reflection of light
this takes place because light is
travelling from a denser to a rarer
medium in this case from water to air
and the angle of incidence of light is
greater than the critical angle of water
so instead of refracting all the colors
get reflected back and now the seven
colors again try to lead the raindrop
this time the angle of incidence is
lesser than the critical angle so there
is refraction of light and that's how we
see the seven beautiful colors of the
rainbow as we've learnt light is made up
of many different colors but if light
wasn't so colourful it would be like
watching an old black-and-white movie
but we don't want that right so let's
get the colors back on and now are you
ready for the top three questions on
this topic coming up for you right now
friends try solving these questions and
let me know your answers and doubts by
putting it in the comments below I
promise to reply to all your comments as
soon as possible
so I'm going to disappear and you pause
the video here and get these questions a
shot friends I hope you enjoyed this
colorful video so do hit the red
subscribe button for my YouTube
and the blue like and follow button for
my facebook page and do check out my
green website Manoj academy.com hold on
I don't think it's green in color
anyways do take a look thanks for
watching
you
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