What is Infrared Radiation & Electromagnetic Spectrum? - [4]
Summary
TLDRIn this episode of '10 Minute Science,' viewers are introduced to the concept of infrared radiation, a type of electromagnetic wave associated with heat. The video explains how infrared radiation was discovered by William Herschel, who found that the temperature increased beyond the red spectrum, indicating the presence of invisible light. It also covers the electromagnetic spectrum, the relationship between wavelength, frequency, and energy, and how infrared radiation is used to detect heat, even in the dark. The script concludes by pondering the unknown aspects of the universe that remain undiscovered due to our limited sensory and technological capabilities.
Takeaways
- 🌡️ Infrared radiation is associated with heat and is radiated by all objects, even those not visibly glowing.
- 👀 Infrared light is invisible to the human eye but can be detected with specialized cameras or instruments.
- 🏠 The script uses images to demonstrate how infrared radiation can reveal heat leaks in a house and the relative temperature of different areas.
- 🤒 Infrared radiation can be used to detect fever in humans, as an elevated body temperature emits more infrared radiation.
- 🔬 The electromagnetic spectrum includes a range of wavelengths, with infrared lying just beyond the red visible light.
- 🌈 The visible light spectrum is just a small part of the entire electromagnetic spectrum, which also includes radio waves, microwaves, and gamma rays.
- 🔍 The discovery of infrared radiation by William Herschel was accidental, as he noticed higher temperatures beyond the red light when using a prism and thermometer.
- ⚫ The black body curve illustrates how objects radiate energy at different wavelengths according to their temperature, with infrared often being more prevalent than visible light.
- 🔆 Even though violet light has higher energy photons, the sun emits fewer violet photons than red or infrared, affecting the temperature readings in Herschel's experiment.
- 🔬 Quantum mechanics tells us that the energy of a photon is related to its frequency, with higher frequencies corresponding to higher energies.
- 🌌 The script ends with a thought-provoking question about the unknown aspects of the universe that we may be unaware of due to our limited sensory and technological detection capabilities.
Q & A
What is infrared radiation?
-Infrared radiation is a type of electromagnetic radiation that we associate with heat. It is invisible to the human eye but can be detected with special cameras and is emitted by all objects with a temperature above absolute zero.
How can infrared radiation be visualized?
-Infrared radiation can be visualized using special cameras that are sensitive to infrared wavelengths. These cameras can create images that represent the relative heat of objects, with colors such as red indicating hotter areas and blue indicating cooler areas.
What does the color in an infrared image represent?
-In an infrared image, different colors represent the relative temperature of the objects being imaged. Reddish colors indicate hotter areas, while bluer and yellow colors represent cooler areas.
How was infrared radiation discovered?
-Infrared radiation was discovered by William Herschel in 1800. He found that there was a type of invisible light beyond the red end of the visible spectrum that caused a thermometer to register higher temperatures than the visible light.
What is the electromagnetic spectrum?
-The electromagnetic spectrum is a range of all types of electromagnetic radiation, arranged by wavelength or frequency. It includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
Why can't we see infrared radiation with our eyes?
-We can't see infrared radiation with our eyes because the chemistry of our eyes is sensitive only to a specific range of wavelengths known as the visible spectrum. Infrared wavelengths are longer than the red light that marks the limit of our visible range.
What is the relationship between wavelength, frequency, and energy of electromagnetic waves?
-The relationship between wavelength, frequency, and energy is such that as the wavelength gets longer, the frequency gets lower and the energy of the photons decreases. Conversely, as the wavelength gets shorter, the frequency gets higher and the energy of the photons increases.
How does the sun emit different frequencies of light?
-The sun emits light across a wide range of frequencies. However, it does not emit all frequencies equally. The distribution of frequencies emitted by the sun follows a pattern known as a blackbody curve, which has a peak and then gradually decreases on either side.
Why does a thermometer measure higher temperatures in the infrared region compared to violet light, even though violet photons have higher energy?
-Although violet photons have higher energy than infrared photons, the sun emits fewer violet photons than it does red or infrared photons. The temperature measured by a thermometer is influenced by the total energy from all photons hitting it, not just the energy of individual photons.
What is the significance of the discovery of infrared radiation in relation to our understanding of the universe?
-The discovery of infrared radiation expanded our understanding of the universe by revealing that there is more to the electromagnetic spectrum than what is visible to the human eye. It also highlighted the fact that objects emit radiation based on their temperature, which is crucial for technologies such as thermal imaging and understanding celestial bodies.
What are some applications of infrared technology that we use today?
-Infrared technology is used in various applications today, including thermal imaging for detecting heat signatures, night vision for military and security purposes, remote controls for electronics, and in astronomy for studying stars and other celestial objects.
How can the concept of infrared radiation be used to detect fever in humans?
-Infrared radiation can be used to detect fever in humans by measuring the heat emitted by the body. When a person has a fever, their body temperature increases, and so does the amount of infrared radiation they emit. Specialized infrared cameras can capture this increased radiation, indicating a fever.
What is the connection between infrared radiation and the study of dark matter and dark energy?
-The connection between infrared radiation and the study of dark matter and dark energy is that they all represent aspects of the universe that are not directly observable with our senses or current instruments. The discovery of infrared radiation, which was initially undetected, has led to the exploration of other phenomena that may be present but currently beyond our detection capabilities.
Outlines
🌡️ Introduction to Infrared Radiation
The video begins with an introduction to '10 Minute Science,' a series that explores scientific topics in a concise manner. The main focus of this episode is infrared radiation, its definition, discovery, and relevance. Infrared radiation is associated with heat and is invisible to the human eye. The host promises to explain how it can be visualized and why it is significant. The explanation begins with a look at images that represent different temperatures through color variations, indicating heat loss through windows and good insulation in a house. The concept is further illustrated by showing how a radiator and a person with a fever emit infrared radiation, which is detectable even when visible light is not.
🔬 The Electromagnetic Spectrum and Infrared Discovery
This paragraph delves into the electromagnetic spectrum, explaining the range of wavelengths that make up different types of electromagnetic radiation, from radio waves to gamma rays. Infrared (IR) radiation is positioned just beyond the red light in the visible spectrum. The discovery of infrared radiation is attributed to William Herschel, who in the early 19th century, observed that there was a region of the spectrum beyond red light that was particularly warm. His experiments involved using a prism to disperse sunlight and a thermometer to measure the temperature increase at different points in the spectrum. Herschel's accidental discovery led to the understanding that infrared radiation is a form of electromagnetic radiation that we cannot see but can detect as heat.
🔍 Herschel's Experiment and Infrared Detection
The script recounts William Herschel's experiment in detail, where he used a prism to split sunlight into a spectrum and measured the temperature at various points. Herschel found that the region beyond red light, now known as infrared, registered a higher temperature than any of the visible colors. This indicated the presence of an invisible form of light that had a warming effect. The host also shares a personal anecdote about replicating Herschel's experiment during a science fair, which confirmed the presence of infrared radiation beyond the visible red light, as it registered a higher temperature than the visible spectrum colors.
⚫️ The Black Body Curve and Sun's Radiation
The explanation continues with the concept of a black body curve, which describes how objects at a certain temperature emit radiation across the electromagnetic spectrum. The sun's radiation is used as an example to illustrate that not all frequencies are emitted equally; some are more intense than others. The sun emits more infrared radiation than ultraviolet light, despite the fact that individual ultraviolet photons have higher energy than infrared photons. This discrepancy is due to the lower number of high-energy photons compared to the higher number of lower-energy ones. The sun's radiation is also discussed in terms of the spectral irradiance, showing that the sun emits a wide range of wavelengths, with visible light being only a small part of the sun's total output.
🌌 Infrared Radiation and the Universe's Hidden Aspects
The final paragraph emphasizes that infrared radiation is a form of electromagnetic radiation like any other part of the spectrum, but with a longer wavelength. It reiterates the accidental discovery of infrared by Herschel and its association with heat, explaining that all objects above absolute zero temperature emit infrared radiation. The host concludes by pondering the unknown aspects of the universe that we may be unaware of due to our limited sensory and technological detection capabilities, hinting at phenomena like dark matter and dark energy. The video ends with an encouragement for viewers to continue exploring and learning about science.
Mindmap
Keywords
💡Infrared Radiation
💡Electromagnetic Spectrum
💡Wavelength
💡Frequency
💡Photons
💡William Herschel
💡Calorific Rays
💡Black Body Curve
💡Spectral Irradiance
💡Thermometer
💡Quantum Mechanics
Highlights
Infrared radiation is associated with heat and is radiated by all objects around us.
Infrared radiation is invisible to the human eye but can be detected with special cameras.
Different colors in thermal images represent relative temperatures, with red indicating hotter areas.
Infrared radiation can reveal heat leakage through windows and good insulation in a house.
A sick person with a fever can be identified through the infrared radiation emitted by their body.
The discovery of infrared radiation is attributed to William Herschel in the late 18th century.
Herschel discovered infrared by measuring temperatures of different colors of light from the sun.
The electromagnetic spectrum includes a range of wavelengths from radio waves to gamma rays.
Infrared radiation falls just beyond the red visible light in the electromagnetic spectrum.
The energy of a photon is related to its frequency, with higher frequencies having more energy.
Infrared radiation is associated with lower energy photons due to its longer wavelengths.
The sun emits more infrared photons than ultraviolet ones, despite their higher energy per photon.
Herschel originally called infrared radiation 'calorific rays', relating it to heat.
Infrared radiation is not a 'heat ray' but an electromagnetic wave like visible light and other spectrum types.
Every object above absolute zero temperature radiates energy, including infrared.
Infrared radiation can be detected even when an object is not emitting visible light.
The video concludes with a thought-provoking question about undiscovered aspects of the universe that we may be ignorant of due to our current detection limitations.
Transcripts
hello welcome back to 10 minute science where we take a topic we dissect it and we learn about
something amazing in 10 minutes or less but remember that's plus or minus 12 additional
minutes so what we have today we're going to learn about the concept of infrared radiation
what is infrared radiation and also how was it discovered and why do we care I promise it'll
be worth your time to stick with me till the end so infrared radiation is the radiation that we
associate with heat of a body so everything around you is radiating these invisible Rays
we call infrared Rays or infrared radiation let's take a look at a few pictures in the first picture
here we have a house now the different colors here are telling us the relative temperature
the relative the relative temperature hot or cold the reddish colors are the hotter aspects and the
Bluer and the yellow are the cooler areas now we can see that the uh the walls there near the
windows are actually red and that means that we can see a lot of heat coming through the windows
and that means basically heat is leaking through the windows it's not a very good insulator around
the windows but we see up around the walls and the other areas near the top of the image that
it's not quite so red and that means that there's a lot of really good insulation there keeping the
heat in the house so anywhere we see red we see heat uh leaking out of the house now it seems
kind of amazing that you can see heat what we're seeing is the infrared radiation coming from that
heat you can see that actually the chimney on top of the house you can see a little bit of yellow
and a little bit of red there as well because of course you know the chimney leaks heat out
that's what it's supposed to do all right let's take a look at image number two where we have the
interior of our house we have a window and at the bottom of the image we have a radiator to
heat the house up in the winter time now we can see that the window is blue which means that the
windows are quite cold because the outside air temperature is cold and when we look underneath
the window we see that the radiator the little uh the white area down there is actually red which
means it's radiating a lot of heat so there's there's a heater going on it's very hot and so we
see that as red so red is hot blue is cold now in the third little thing we're going to look at here
who have some people walking by we have cameras that can sense the infrared radiation and we can
see that most of the people in this image are you know not too hot so we have some some uh some of
the clothes are actually uh cooler the skin is a little bit warmer but there's one person in this
Frame that's actually looks red hot and that person actually is sick with a fever so when
the temperature of the body gets elevated we can actually see it in the form of infrared radiation
coming off the body so the one person there is sick right and then the fourth picture here
uh we can see the head of this woman here and the hair and you can see the hair itself is not
that hot so it's bluish more blue color but the skin itself is is much warmer so the skin is hot
there so how can we see heat that's what we want to come come to the understanding of and also how
is this even discovered because the story behind it is quite interesting all right so in order to
go any farther we need to take the kid gloves off and talk about the answer to this thing we'll get
to the discovery of it in a minute but we're going to talk about the what we know to be true
today so what we have is a spectrum we call it an electromagnetic spectrum you see the waves up here
we'll talk about it in a second here now what you can see with your eyes is a very small sliver of
this thing that which we call the electromagnetic magnetic Spectrum you can see over here we have
the purple or violet or indigo blue and then we have the greens and the yellows and then the Reds
but these are the only uh uh wavelengths we'll talk about wavelength in a second that we can
see from the electromagnetic spectrum and that is just because of the chemistry of our eyes our eyes
have photoreceptors which are we have chemicals in our eyes that react to certain energy photons
and so in that range uh where they're sensitive to then we can when a photon hits we can trigger
a reset we can see the photon essentially but if a photon energy we're going to talk about photons
in a second a little more Falls outside of this visible bandwidth there this is visible range
then the chemistry is not triggered so we can't see infrared but we can build machines cameras
that are sensitive to infrared and the other uh the other aspects of the spectrum now I'm going
to do a whole video on the Spectrum but just in a nutshell you notice you have radio waves
now we have this wave up here notice that the wave is very stretched out we say it has a very
long wavelength over here right and in fact these are this is you know very very long this is meter
so this is you know this is a hundred meters here here's in the thousands of meters over here these
radio waves can be very very long then we have am and F M waves that you can use for the radio Wi-Fi
microwave is actually a centimeter wavelength and then we have infrared IR which Falls just
on the other side of red here and then we have the visible spectrum now we start to get into
shorter wavelength electromagnetic waves and then on the other side of violet we have ultraviolet
so flanked on each side of the visible spectrum on the one side of red we have infrared and on
the other side of violet we have ultraviolet I know you've heard of ultraviolet because that's
what we have to protect ourselves from the Sun from getting a sunburn now on the other side
of that we have x-rays which are high energy and gamma rays which are even higher than that
now the one thing I want to point out because it's going to become important later in the
lesson is and I'm going to do an entire lesson on the electromagnetic magnetic Spectrum another
day but for now just know that it consists of waves which can differ in wavelength so we have
long waves over here and when I mean wavelength I mean these are a waves that oscillate right and
in space and in time and so the wavelength which we call Lambda is the distance over which a wave
begins to repeat so notice it goes up down and it begins to repeat again that's one wavelength and
it's literally measured in meters okay so these waves over here are very long this is like a this
is 100 meters this is like a thousand meters over there and even longer and then we have centimeters
which are in your microwave so the microwave oven has a little centimeter length waves and then we
have visible which are basically this is measured in uh billionths of a meter so we'll talk about
that in a second I have another slide and then we have even shorter and shorter and shorter
but notice that as the wavelength gets shorter because the wave is actually getting shorter
then the frequency which is on the top gets is getting bigger so frequency is how much something
is oscillating and you can see over here it's not oscillating very much or very fast so to speak
but over here these gamma rays and x-rays are oscillating very very fast so the wavelength and
the frequency are they go opposite of each other as the wavelength gets longer the frequency gets
uh or the wavelength gets bigger the frequency gets lower and lower because it's not oscillating
much and as the wavelength it's very very small the frequency gets very very fast all right and
the other thing that we're going to talk about a little bit later is that as the frequency gets
higher and higher and higher the energy of each of these photons because electromagnetic waves come
in packets that we call photons we discovered that along with the Advent of quantum mechanics these
waves do not just travel like waves in the ocean they come in packets like little little buckets
that hit the hit your eye and hit the detector which we call a photon of course there's an
oscillating aspect to it but they come in packets we call photons and because these are oscillating
faster these have what we call higher energy so as you look at this chart this is lower energy
medium energy and higher energy and over here the gamma arrays are the highest energy photons
you may have heard of gamma radiation or x-ray radiation that's the highest energy photons
that we know about there but all of these are basically different flavors of the same thing
they are flavors of electric and magnetic fields which are oscillating we call electromagnetic
waves all right I have one more chart to drill that home here this is basically the same thing
it's the same thing as what was there just with numbers showing that the visible spectrum Falls
from 400 nanometers of wavelength remember a nanometer is a billionth of a meter so 400
billionths of a meter very very small wavelength but this is a larger wavelength over here it's
the same picture as this it's just kind of hard to read these numbers here and this is so small
here and what the exponents is very difficult so we often talk about wavelengths of light
in terms of nanometers so you see the smaller wavelength here bigger one going this direction
all right so now that we know that the visible light that we can see is only a tiny fraction
of everything that's out there that we can't see uh but in in uh the time when infrared light was
discovered we didn't know of anything that existed other than the visible light okay now anything uh
that we say uh on the other side of here we call it infrared and on the other side of violet we
call ultraviolet said that and uh we want to talk about now how it was discovered because
the discovery of infrared light is actually really really fascinating so there was a scientist named
William Herschel he lived from 1738 to 1822 and he was doing astronomy so we had a telescope and
he was actually looking at the sun or measuring the Sun that not a not a uh I don't advise you to
do that because you can damage your eyes but he was using filters on his telescope to try
to to see what kind of light the sun was actually emanating and coming and sending to Earth and what
he thought he was seeing through his telescope when he would put different filters in front
of the telescope is he thought that uh he was sensing that the red light when he would isolate
the red light from the telescope he thought that it felt warmer to his touch than the blue light
for instance when he would put the blue filter in front of the telescope so he started getting
curious about the temperature of the different current uh wavelengths of light that are being
sent and are what what is the temperature distribution which one is hotter and which
one is colder right so we wanted to investigate that now in order to investigate it further what
he did is he put the telescope away and he or I guess he focused it through a telescope took the
light from the sun and passed it through a prism now you can see what's going to happen we've all
done this we know that when we take sunlight which is all of this stuff here and we put it through a
prism it breaks it up into the Spectrum right we can see the different colors there and what
he did is he tried to measure the temperature of the different colors so he would literally take a
thermometer and he would take the bulb of it and bulb of the thermometer and Blacken it with black
paint the reason he did black paint is because it was known that black colors absorb more radiation
and you know that as well today and what he would do is he would physically put this thermometer
here and here and here and here and here and then uh measure the temperature of the of a different
light coming from the Sun and what he figured out is that this violet color was cooler and as
he would move the thermometer this way towards red it got warmer and warmer and warmer here
and then just by accident see what he was trying to do was do a controlled experiment so he would
put one thermometer in the purple and he would put one thermometer outside of the spectrum
just as a control to see what the Ambient Air Temperature was out here so he would put one
thermometer in here and one thermometer here but we know now that on the other side of this uh red
is infrared so what is the thermometer on the outside was doing was measuring the temperature
of the infrared photons that he couldn't see with his eyes but but that were that was hitting his
uh his detector here his thermometer and what he figured out is that the infrared thermometer was
actually getting hotter than any of these other colors and hotter than the air temperature so he
knew that there had to be some sort of invisible light that he couldn't sleep with his eye that
was hitting this thermometer and that's kind of amazing it was discovered totally by accident
infrared and then later we learned that there's even more than infrared that exists out of there
all right now he originally called this infrared light just just as a historical interest he called
it calorific Rays now you can think of calorific being similar to calorie and which kind of means
heat and so that's kind of where that comes from we don't call it calorific Rays anymore we call
it infrared radiation because it's right on the other side of red and the visible spectrum now as
chance would have it when my daughter was doing the science fair years ago we reproduced this
experiment I actually did it in the backyard took a box took sunlight refracted it through a prism
we could see the rainbow and we would carefully measure the temperature of the different colors
and then also the infrared and I'm going to write down the numbers that we got even though
it's not that super important but I think it's it's it's useful to see so what we saw is that
for the violet color we measured 80 degrees Fahrenheit now apologize for Fahrenheit I
don't like the Fahrenheit temperature scale it's the only thermometer I had available that day so
that's why we use that there and then when we get over here to Yellow over here we were measuring
around 84 degrees Fahrenheit and just a smidge higher it was very hard to read the difference
between yellow and red here but when we put the thermometer outside of red right here in the
infrared region we actually measured 86 degrees Fahrenheit so we sort of reproduced herschel's
experiment which is the whole point of you know of why we did it and we could see that that was true
all right now I've actually done a similar video to this in the past and a lot of students sent
me comments because I told you that we got the lowest temperature on Violet and then
medium temperatures over here and infrared was the highest temperature but then those of you
that know a little bit about quantum theory you know that the energy of a photon of an individual
photon is what we call HF this is just Planck's constant this is planks constant it's just a
number so don't worry about what it is right now it's just a number times F which is the frequency
of the wave so you can see that that these very long uh these long wavelengths this is very
low frequency so because it's a low frequency it's a low energy Photon so this is low energy
low energy Photon but as we go this way higher and higher frequency higher and
higher frequency higher and higher frequency the frequency is getting higher this is just
a number so the energy of every photon is higher as the frequency gets higher and it
makes sense when you think about it because the wiggling is very very very very fast so
it makes sense that it would be a higher energy so over here we have high energy
high energy Photon so the same thing is true of the visible this is higher energy than
this because the frequency here is higher than the red and higher than the infrared so let me
ask you a question if we know the energy of the Violet should be higher than the energy of the
red if we know that to be true from math from quantum mechanics which we know is true it's
a very accurate Theory then when I measured the temperature why did I measure a low temperature
here and a high temperature here it doesn't make any sense well there's one more piece
of the puzzle again I'll do a totally separate video later but one more piece of the puzzle
that we want to talk about to understand that and that is how does the sun actually broadcast
all of this energy to Earth because it doesn't broadcast all the frequencies the same that's
the punch line so what we can measure uh and we can measure this in the lab we can measure
that we can calculate it also with quantum mechanics if we plot the wavelength this is
Lambda the wavelength in nanometers right uh and we can on this axis we can call that the spectral
uh irradians I'm going to put irr for irradians because the units don't really matter I could
write it's watts per and there's some other units it doesn't matter so much what it turns out is
everything in the universe including the Sun at a certain temperature radiates according to what
we call a black body curve it looks something like this it goes up to some Peak and then it
drags down gradually on the other side like this so you see this is a plot of wavelength this is
very low wavelength long wavelength light like what's over here very long wavelength and then
here we have a a very uh I'm sorry I said that backwards we have very short wavelength light
which is over here short wavelength line over here and very long wavelength like like radio waves and
things like that over here very long wavelengths over here now what I want to do is I want to put
two little X's right here one right here and one right here and I'm going to draw a little dotted
line down here and this is from the Sun our sun whoops I can spell Sun correctly son like this
and I'll draw a little dotted line down here right what we have is this region here is the visible
right and then on the other side of visible higher
energy is what we call ultraviolet and then over here this is infrared
but don't forget that as you go farther Beyond infrared just like over here like this is infrared
right here you have microwaves and radio waves and all this other stuff so you have all kinds
of radio waves way over here as well when you get long wavelength but the point is is the
entire visible spectrum that the sun radiates to Earth it's not radiating all frequencies
this this is the same amount right the uh uh the shortest wavelength that we have right here the
shortest wavelength which is the the purple or the Violet I guess I should say this is violet
and this is red because it's longer wavelengths longer wavelength is red and then you get to
infrared right so notice what's going on even though every Photon of violet light has more
energy than every Photon of red light that is true however you can see according to the graph the sun
is sending a lot less Violet photons to Earth than red and then Infrareds are on the other
side of it but infrared is still higher than the violet light so I'm going to say that one
more time because I've probably got thousands of comments about this it is true that violet light
violent photons and UltraViolet photons have a higher energy because of this equation right
Planck's equation higher energy per photon than all of the red in the infrared light that's true
every Photon for a violet and UltraViolet is more energy however the sun is not sending as many of
those photons to the Earth and when I measure the temperature of these different colors what you're
doing is it's all the photons are hitting it and and the energy is going in there and then making
the thermometer do it it's thing and you can read it but if there's not that many of these photons
the temperature is not going to be as high so even though the data is sort of completely backwards
than what we know reality to be the point is Herschel put his thermometer outside of this
region and he was able to detect like that he couldn't see at all so that is the last thought
I want to leave you with infrared radiation is associated with heat because everybody in the
universe even if it's not reflecting any actual light even if it's in the dark like a human
being in the dark totally dark room if you could look at them in the infrared you're going to see
infrared radiation why because I'm again I'll do a whole nother video on it but everybody in the
universe at any temperature above zero is going to be radiating energy and some of that energy
is going to be infrared even if it's not radiating any visible light it will always be able to you'll
always be able to detect some photons other than visible photons uh there so for instance if you
put a a poker in the uh in the fire the campfire if you make it red hot and hold it up you see
the red color it's radiating red but it's also rating radiating infrared but as it cools down
right as it cools down then you don't see as much of the red color but it's still hot so in
an infrared camera we're still going to see some infrared light there even though the visible isn't
radiating as much because the infrared photons are are not being able to be detected by your eye all
of this energy all of it is coming from atoms and the electrons going up and down in their orbits
and when the electrons fall back into an orbit they radiate a photon away so even if it's not
visible to you the infrared radiation is coming because electrons can fall in orbits and emit
an infrared Photon in the wavelength range that we've outlined here just beyond uh just beyond the
um the 700 nanometer range those will be the infrared photons so even if the the poker is
not emitting visible light which would be higher energy it can still be radiating infrared light
so that's why we associate infrared with heat it doesn't mean the infrared is like a heat ray or
a different kind of Ray or something different it's still an electromagnetic wave just like
light just like ultraviolet just like radio waves just like microwaves just like gamma rays you see
I can go on and on just like Wi-Fi right it's still a photon of electromagnetic radiation the
only difference is the reason we associate it with heat is because if something is warm but
not visible like that poker that is still hot from the from the fire but not glowing it can still be
uh radiating infrared photons over here but maybe we're not seeing the visible because this entire
curve as the temperature of the object changes this curve shifts around so maybe maybe we're
not seeing any of the infrared Photon anymore but we can we're not seeing any more of the visible
photons anymore but we can still be seeing the infrared photons so the takeaway here is
infrared light is light just like any other color of the spectrum it just has a longer wavelength
and red light and the way it was discovered was absolutely by accident by William Herschel now
the last thought I'll leave you with is what other aspects of our universe are we completely ignorant
of just because we can't detect it with our senses or our computers or our instruments you know we're
wrestling with questions like dark matter dark energy that we don't interact with we don't see
or interact with dark matter it must be around us but we don't interact with it that's the problem
we don't sense it because it it must not interact with normal matter the same way that light for
instance interacts with matter light bounces off of everything okay but we know about that because
we can sense it what other things are out there that we can't even sense that we're completely
ignorant of just because we don't have the proper equipment on our body or in our computers to
detect it that's what I want to leave you with for our last thought there so thanks for taking this
ride with me on infrared radiation I encourage you to learn more about amazing science Concepts
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