Lesson video

Hello and welcome to this lesson called Dispersion of Light and Electromagnetic Radiation.

This is from the unit called Electromagnetic Waves, and my name's Mr. Norris.

Now, people have always been fascinated by seeing a rainbow in the sky or perhaps a rainbow in a waterfall or something like that.

And in this lesson we're gonna look at what rainbows are, the colour spectrum of light caused by dispersion, the light being dispersed, but we can also go beyond a rainbow and look at the full spectrum of light.

So that's what we're gonna study in this lesson.

Let's get going.

Here's the outcome for today's lesson.

By the end of the lesson, hopefully you'll be able to explain what's meant by the visible light spectrum and the spectrum of electromagnetic waves.

Here are some key words that will come up this lesson.

Electromagnetic waves, frequency, spectrum, refraction, and radiation.

And each word will be explained as it comes up in the lesson.

This lesson is split into two sections.

We're firstly gonna focus on the visible light spectrum and then we're gonna go beyond the visible spectrum.

Let's get going with the first section.

So light can be thought of as a wave.

And waves occur when something is disturbed or made to oscillate, and then the disturbance or oscillation travels.

So like this rope here is being disturbed and made to oscillate and the disturbance or oscillation travels down the rope.

But light waves are electromagnetic waves.

So they're similar to those waves on a rope or waves on a string, but they're different because they're not oscillations of a rope, they're not oscillations of an object, they're oscillations or ripples in invisible electric and magnetic fields that are all around us.

So what do light sources, things that give out light, what do they actually do? Well, they disturb nearby electric and magnetic fields a bit like what was disturbing that rope, except this is done to invisible electric and magnetic fields.

So the ripples from a light source, the ripples in electric and magnetic fields travel outwards, transferring energy, and that's what light is.

Let's just go over some ideas about waves.

So the frequency of a wave is the number of oscillations that are happening per second, and that also gives the number of waves that arrive at a point per second.

So that's the frequency which is measured in hertz, capital H, little z for hertz.

And then the amplitude of a wave is the maximum displacement of a wave from the undisturbed position.

And the wavelength of a wave, which is given that Greek symbol, symbol lambda, that is the distance between one point on a wave and the same point on the next wave.

So I've gone peak to peak here, but it doesn't have to be peak to peak, it could be trough or trough or any point on a wave and the distance between the same point on the next wave.

So the waves in that animation were transverse because the oscillations were up and down, but the waves were going along.

So the proper definition of that is you can't just say up and down and along, you've got to give that angle.

The oscillation is at 90 degrees to the direction of energy transfer.

So electromagnetic waves like light waves, they are transverse oscillations in electric and magnetic field.

So the direction of oscillation is 90 degrees to the direction of energy transfer.

And what's important to remember is electromagnetic waves can have any frequency.

And that's what the different colours of light are, the different colours of light are just electromagnetic waves with different frequencies.

You can see in the diagram there's a visible light spectrum or a rainbow, so it's called a visible light spectrum, with a little frequency scale, that's rough, it might not be quite exact, but it's been drawn on to indicate the different frequencies that the different colours of light have.

So a rainbow pattern of coloured light like this is called a visible light spectrum.

We need to get used to using that word spectrum.

But of course, the word spectrum just means a continuous range or scale.

If something is on a spectrum or there's like a spectrum, then that just means there's a range to choose from and it might be a continuous range or scale.

So a visible light spectrum shows the full range of colours, frequencies, that visible light waves can have.

It shows the full spectrum, all the possible frequencies of visible light.

So let's do a check on that.

Rainbows are said to contain seven colours traditionally, but in reality there's a continuous spectrum, there's a continuous range of colours.

So, can you have a go at these two questions just to check your understanding of what we've just said so far? Pause the video now and then I'll see you once you've had a go at answering these two.

Right, I'll give you some feedback now.

So the order of the seven colours of the rainbow kind of traditionally are red, orange, yellow, green, blue, indigo, violet.

And which colour of light has the lowest frequency and which has the highest? Well, the lowest frequency is red light and the highest frequency in the spectrum, if we go through the seven colours of light in the rainbow, is violet light.

Well done if you've got that.

Now, let's talk about wavelength briefly.

The wavelength of any wave is set by the wave equation, wave speed equals the frequency times the wavelength.

But of course, in air or a vacuum, all electromagnetic waves, so all light waves, have the same speed.

That's 300 million metres per second or three times 10 to the eight metres per second.

So what that means, if frequency times wavelength always gives the same speed, then if waves have a higher frequency, they must have a lower wavelength to multiply to give the same speed.

So the bigger one gets, the smaller the other one gets by the same proportion.

They're inversely proportional, frequency and wavelength for electromagnetic waves.

So when one increases, the other decreases to the inverse proportion.

So for example, a light wave with double the frequency would have half the wavelength.

Look at the diagram and make sure you're clear that the frequency scale runs upwards from red to blue, but the wavelength scale gets shorter from red to blue.

Okay, let's do a check of what we've just said.

So starting at red and moving through that spectrum to violet, in what order do the different colours of light appear? Choose the ones you think, off you go.

Okay, I'll give you some feedback now.

So starting at red and moving through the colour spectrum to violet, the colours appear in order of increasing frequency 'cause red light has the lowest frequency and violet light has the highest frequency.

The speed in air is the same for all electromagnetic waves, for all colour of light, so it's not C or D, but it's also order of decreasing wavelength 'cause red light has the longest wavelength and violet light has the shortest wavelength.

Well done if you've got both of those.

So the sun and standard light bulbs give out white light, but white light is really a mixture of all the different frequencies, all the different colours of visible light.

So white light is really all the colours of light combined.

And this can be proved by passing white light through a triangular glass prism to produce a visible light spectrum like we've just seen.

So there's some white light going into this prism, and a prism will split up the white light into a visible light spectrum like that.

That effect is called dispersion.

You can say the white light has been dispersed into the different colours.

And just to prove that white light really is made up of the different colours of light, a second prism can then recombine the separated colours back into white light, like this.

There's a second prism and it recombines the colours back into white light.

And that experiment was first performed and explained by Isaac Newton in about the year 1670.

Okay, let's do a check on what we've just said.

Which best explains this effect? Pause the video now and choose which option you think.

Okay, the option that best explains this effect is option C.

The prism splits up the white light into the different colours that the white light's made from.

It's not option D.

The red light does refract less and the violet light does refract more, but the white light didn't change colour to red and violet, the red and violet was already there just in the white light ray and the prism split up those different colours.

So well done if you said C.

So dispersion occurs because different frequencies of light have different speeds in some materials, and that's why they refract through different angles.

Refraction also changes the wavelength of the waves, but not the frequency.

And the frequency, remember, links to the colour.

So this is why we've always been talking about colours of light having different frequencies because the frequency of a colour is set.

The wavelength of that coloured light wave can change in different materials, but the frequency of a certain colour never changes.

So it's the frequency that's links to the colour and wavelength of that wave can change depending on the material.

So higher frequency light waves, like violet for example, they refract more because they travel slower in a medium like glass.

That's what makes them refract more.

Now, in a rectangular glass block, this effect of dispersion is barely noticeable.

It does happen, but it's barely noticeable because the rays leave the block parallel and very close together.

When rays are refracted as they enter the block, they're refracted through a certain angle, and when rays leave the block, they're refracted back the same angle.

So whatever angle each coloured ray or each colour of light is refracted on the way into the block, on the way out to the block is refracted back exactly the right amount, so all the rays are still parallel, again, when they leave the block.

So that's where the effect is barely noticeable in a rectangular block.

Whereas in a triangular prism rays are refracted twice in the same direction because of the shape of the prism.

So that means the different colours leave the block at different angles and spread apart, and that's how you can end up with a colour spectrum on the other side of that triangular glass prism.

Okay, let's do a check on what we've just said.

So the diagram represents the refraction of red light by a triangular prism.

Which of the following properties of the red light stays the same during this process? Look carefully at the diagram.

Five seconds, decide now.

Okay, the only property that stays the same is the frequency.

The wave speed changes because glass slows down light waves and the wavelength changes.

The only thing that's set about red lights is the frequency.

And part two of this check, how would this diagram be different for violet light, which is incident along the same initial path? Pause the video now and choose between the options.

Right, I'll give you some feedback now on this one.

So refraction would not occur in the opposite direction.

Refraction is gonna occur in the same direction as for the red light, so not A.

The changes in angle, though, would be greater because violet light is high frequency, so slows down more in glass, so refracts more.

Now, the wavefronts in air would be closer because violet light does have a shorter wavelength in air.

So that's right, well done if you said C.

And the wavefronts in glass would also be closer, and that's true as well because violet light is slowed down more by glass than red light, therefore the wavelength shortens in the glass too.

So well done if you said B, C, and D.

And then here's a version of what that would look like.

Well done if you got that right.

Okay, time for a task now on this section of the lesson.

This task has five sections.

Here are the first three.

They should be fairly straightforward to do, so short answers for those.

And part four and part five.

Part four is completing a diagram and part five is using some terms to fill the gaps in the text.

Pause the video now and give each part of that task your best effort.

Do go back one slide to see parts one, two, and three of this task if you need to.

See you in a few moments.

Okay, I'll give you some feedback on these now.

Now, questions one, two, and three were fairly straightforward, so I'm just gonna pop the answers up and you can compare your answers to mine and make any improvements to your own.

Pause the video now.

Okay, and now for parts four and five.

Part four should be fairly straightforward to label that diagram.

And part five, the correct gap fills are coming up on the screen now.

So again, pause the video and make any corrections to your work.

Well done for your effort on that task.

So that takes us to the second section of the lesson.

So we're now gonna go beyond the visible light spectrum to look at other frequencies that electromagnetic waves can have.

So human eyes can only detect electromagnetic waves in a limited frequency range, only between about 400 terahertz and just under 800 terahertz.

Now, one terahertz is a million million hertz, so that's a very high frequency.

So the frequency of visible light waves is very, very high.

But what about all of the frequencies below 400 million million hertz or below 400 terahertz? What about all the possible frequencies that are above 800 million, million hertz, 800 terahertz? 'Cause electromagnetic waves can have any frequency.

So electromagnetic waves with higher or lower frequencies, they're not detected by the human eye.

So they can be thought of as the same thing as light, but it's not light because you can't see it.

It's not visible light, it's the invisible kinds of light.

So let's look at some examples of that.

So electromagnetic waves, the same thing as what light is, but with frequencies in a range just lower than what the eye can detect, so just lower than red light, they're called infrared waves.

And the word infra means below.

So infrared electromagnetic waves are electromagnetic waves with a frequency that's just below the frequency of red light.

And electromagnetic waves with frequencies in a range just higher than violet light, so just higher frequency than the eye can detect, they're called ultraviolet waves.

And ultra means beyond, so these are waves which are just beyond violet visible light waves in frequency.

So white light from the Sun, we know it contains all of the frequencies of visible light, but it actually contains lots of infrared and ultraviolet frequencies of electromagnetic wave, as well as those visible frequencies.

And you've probably heard of the Sun's ultraviolet rays because that's what can cause sunburn if you stay in the Sun for too long.

But we're gonna firstly talk about the infrared waves that are in sunlight, and they can actually be detected by a sensitive thermometer placed just outside the red end of a visible light spectrum, like in this diagram.

So look really carefully about where that thermometer's being placed.

It's outside of the beam of red light, but its temperature is being caused to go up when you put it in that position.

It must be something to do with the beam of sunlight, which is split into the visible colours of light, but also the invisible frequencies of light, like infrared.

So this is the path that infrared frequencies would take straight into the thermometer.

So each frequency present in sunlight we know has a different speed in glass, so it's going to be refracted a different amount.

Infrared frequencies are lower frequency than red light, so they're slowed less and refracted less than the red light is.

And the thermometer bulb is quite good at absorbing infrared frequencies, so its temperature increases when it's placed in the path of the infrared.

Let's do a check of what we just said.

Now, sunlight contains ultraviolet, as well as infrared and visible light.

Now, the ultraviolet in sunlight would take the path shown in the diagram through the prism.

So, which of these following statements must be true? A, B, and C.

Pause the video now and decide which you think are true.

Okay, I'll give you some feedback now.

Statement A, ultraviolet waves have higher frequencies than violet light.

Well, we should know that's true because ultraviolet literally means beyond violet.

So they have higher frequencies than violet light, so that's true.

Statement B, ultraviolet waves are faster than visible light and infrared in any medium.

Now, that's not true because ultraviolet waves have the same speed as visible light and infrared in air, so that's not true.

And C, ultraviolet waves are faster than visible light and infrared in glass.

Now, that's not true.

The reason ultraviolet waves are refracted more is because they are slowed down more by glass, so they're actually slower than visible light and infrared in glass.

So only statement A was true.

Well done if you've got that.

So really important idea now.

It turns out that all objects are actually constantly emitting or radiating electromagnetic waves into their surroundings.

That's right, everything in the room in front of you right now, every surface, every wall, the ceiling, every object on the desk in front of you, your own body is constantly emitting or radiating electromagnetic waves.

But the range of frequencies emitted and the intensities depend on an object's temperature.

And at room temperatures and below, objects don't emit any visible lights or higher frequencies than that.

They mainly actually emit infrared, which is invisible, so that's why you can't see everyday objects glowing.

As the temperature of an object increases, the intensity of every frequency emitted also increases.

And also as the temperature of the object increases, the range of frequencies emitted increases to include higher and higher frequencies.

So the hotter an object is, the more infrared is going to emit in a given time for both of those reasons.

And this is what thermal cameras detect, you might have guessed that from the image on the previous slide repeated here.

So infrared cameras, what they actually do is they measure the intensity of infrared from each part of the image, which corresponds to the temperature for the reasons given on the previous slide.

Colours are then added to a thermal image to show each temperature.

So a thermal image does not show us infrared itself, it doesn't show us what infrared looks like, it shows us which areas emit most infrared because they're the areas that should be painted the brightest colours normally on a thermal image, but the colours are added.

And we should make really clear at this point that infrared frequencies of electromagnetic wave are really easily absorbed by lots of different surfaces, including skin.

And that's gonna cause a heating effect when objects absorb infrared from their surroundings or from a hot object nearby.

And that heating effect and the energy transfer is caused without touching because the waves are electromagnetic waves, they can travel through air and through a vacuum really easily.

Now, at around 600 degrees C, and it's the same temperature for all objects, objects start to emit some visible light, as well as infrared, and that's because increasing the temperature of an object increases the range of frequencies emitted.

So the hotter an object gets, the higher the highest frequency is that's emitted, and eventually an object gets so hot that it starts to emit visible light, as well as infrared.

And that's what happens to the heating elements inside a toaster or in the the filament inside a light bulb and the heating filaments of infrared heaters.

Now, they might appear red or orange because they're hot enough to emit some red and orange visible light, as well as the infrared that they're remitting.

Okay, time for a check now about what we just said.

Which of the following objects are remitting infrared? Choose from A, B, C, or D.

And also part two of this check, in which of the images can you see the emitted infrared? Pause the video now and make sure you've got answers for part one and part two of this check.

Okay, let's see how you got on.

Which of the following objects are emitting infrared? They all are.

Okay, we said all objects, whatever their temperature, are always emitting some infrared frequencies of electromagnetic waves into their surroundings.

And in which of the images can you see the emitted infrared? That's a bit of a trick question because none of them, because the infrared itself cannot be seen.

We can see that objects, the hot metal horseshoe and the bold filament, they are obviously hot enough to be giving out some visible light, as well as infrared, but you cannot see the infrared from any object.

It's not detected by our eyes.

Well done if you've got both of those right.

Let's talk a bit more about ultraviolet now.

Light from the Sun also contains ultraviolet or UV frequencies of electromagnetic wave.

And you might already know that exposures to too much ultraviolet, that's what causes sunburn.

And just like infrared, ultraviolet waves are not visible to humans.

Special lamps that emit ultraviolet, they might look like they're violet, but that's because they emit some violet visible light, as well as the ultraviolet they're emitting, which you can't see.

Some insects' eyes can detect ultraviolet, and some flowers reflect the Sun's ultraviolet to attract those insects.

So the top half of this image is a normal photograph of a dandelion flower, the bright yellow flowers you see in grass, and the bottom half of that image is the same dandelion photographed, but it's captured the ultraviolet light.

So it's a false colour image, you're not seeing the ultraviolet there.

Each part, the intensity of ultraviolet reflected from each part of the daisy has been measured and each number has been turned into a colour so we can kind of see which parts of the daisy are emitting most infrared, most ultraviolet, but we're not seeing the ultraviolet itself in that picture.

You can see how those markings, which are only visible in ultraviolet, make a nice target for insects to arrive in the very centre of the flower, probably where most of the pollen is.

And a final thing to mention about ultraviolet is that some substances are fluorescent and that means they give visible light in the moments when they're absorbing ultraviolet light.

And that's how ultraviolet inks work.

And glow in the dark decorations work in a similar way, but they stay glowing for longer after the exposure to ultraviolet has ended.

So the writing in this image was written with ink that's invisible unless it's exposed to ultraviolet light.

So the question is, how does the exposure to the ultraviolet light cause the writing to become visible? Choose from A, B, and C.

Pause the video, off you go.

Okay, time for feedback on this one.

The correct answer was B.

The ink emits visible light when it's exposed to ultraviolet light.

So the ultraviolet light gets absorbed and that causes the ink to give out visible light.

So ultraviolet light is not pinky purple, it's invisible, you can't see ultraviolet.

And that's also why it's not A, because if the ink reflected the ultraviolet that hits it, you still wouldn't be able to see that.

Well done if you've got that one.

So remember that we said that electromagnetic waves can have any frequency.

Well, so far we've only been talking about infrared, visible, and ultraviolet frequencies of electromagnetic wave.

But what about electromagnetic waves which have as low frequency as, say, 100 hertz? Or what about electromagnetic waves which have an incredibly high frequency up to, say, 10 to the 22 hertz? That's a one with 22 zeros after it, number of oscillations per second, frequency of 10 to the 22 hertz.

Well, actually all of these are possible and everything in between 'cause electromagnetic waves can have any frequency.

However, we give electromagnetic waves in different frequency ranges different names because they interact differently with different materials.

So the lowest frequency electromagnetic waves, we call them radio waves.

And that is exactly what carries radio signal and TV signal, signal to a walkie-talkie, Wi-Fi, signal that's carried by radio wave.

And then in between radio waves and infrared waves, that frequency range which is missing, we call those microwaves for electromagnetic waves with those frequencies.

And don't confuse the microwave radiation, the microwave electromagnetic waves with a microwave oven, a microwave oven cooks food using microwave electromagnetic waves, microwave frequency electromagnetic waves.

What about the very high frequency electromagnetic waves? Well, they're called X-rays and gamma rays if they're extremely high-frequency electromagnetic waves.

So this is what I meant at the start of the lesson when we said electromagnetic waves can have any frequency, literally any frequency in this continuous spectrum of possible frequencies.

And just as one example of what I mean by different frequency ranges interacting differently with different materials, we've got the example of glass transmitting visible light, but absorbing infrared.

Whereas some kinds of plastic can absorb visible light, so you can't see through them, they're opaque, whereas they would transmit infrared through them a bit like glass transmits visible light through glass.

So that's what we mean when we say different frequency ranges interact differently with different materials.

So stars, including the Sun, are so hot and large that they produce electromagnetic waves in all seven frequency ranges at detectable intensities.

And you can use that to produce different kinds of images of the Sun by using different kinds of telescopes that detect different frequencies of electromagnetic wave.

For example, that is a radio telescope that detects very long wavelength electromagnetic waves from objects in space.

And remember that the colours in images like this are gonna be false.

They're added by computers just so we can see which parts of the Sun emit each frequency most intensely.

So we'll talk a bit about each of the kinds of, each of the frequencies of electromagnetic wave that we've mentioned.

So the lowest frequencies of electromagnetic wave are called radio waves.

And we've learned how to reduce radio waves to transmit encoded information over long distances.

Radio, TV, phone signal, and Wi-Fi.

Microwave frequencies of electromagnetic wave, they're produced in our homes to cook food in microwave ovens and they're also used for communications.

And then the highest frequency electromagnetic waves are called X-rays and gamma rays.

They're produced from changes in atoms in lots of materials.

An X-ray machine in a hospital can produce controlled bursts of X-rays to create an X-ray photograph.

So X-rays can pass through skin and flesh, but they're absorbed by bone.

That's how you can create a X-ray photograph.

And of course that's different to visible light and other kinds of electromagnetic waves which can't pass through skin and flesh.

Worth mentioning at this point, just a reminder that all frequencies of electromagnetic wave have the same speed in air and a vacuum, which is 300 million metres per second, three times 10 to the eight metres per second.

And what that means is that frequency and wavelength in air are inversely proportional for the entire spectrum of electromagnetic waves.

So when one of frequency and wavelength increases, the other must decrease to the inverse proportion so that the wave equation still works and frequency times wavelength still gives the same wave speed in air.

So here's an example wavelength scale.

You can see that radio waves are the lowest frequency and longest wavelength electromagnetic wave, whereas gamma rays are very, very, very high frequency, but also very, very, very short wavelength, so when you do frequency times wavelength, you still get the speed of light in air and a vacuum.

Let's do a check on some of the things we've just said.

Fill each blank with either the terms wave speed, wavelength, or frequency.

Pause the video now and have a go at that.

There's just three blanks to fill in, off you go, Right, I'll talk you through this one now.

The only difference between each kind of electromagnetic wave is their frequency and wavelength, and they could be either way round.

And all electromagnetic waves have the same wave speed in air and a vacuum.

Final thing we should just mention is that electromagnetic waves can also be called electromagnetic radiation.

Radiation just means something that's emitted and transfers energy away from a system.

So sound waves are acoustic radiation.

You can have a nuclear radiation, and this is electromagnetic radiation, things which are emitted and transfer energy away from a system, electromagnetic waves count as that.

And all kinds of electromagnetic radiation can be produced in nature, for example, by stars, lightning, and hot objects.

Some living things actually produce electromagnetic radiation.

These jellyfish are emitting some visible light.

Electromagnetic radiation from the Sun is naturally present at Earth's surface.

So radiation is a completely natural thing.

Radiation from the Sun is completely natural.

But of course, humans have also found ways of making each kind of electromagnetic radiation.

And the final thing we'll say is that the lower frequencies of electromagnetic radiation, we're talking about radio waves and microwaves and infrared, are not harmful unless the intensity is very high.

The higher frequencies of electromagnetic radiation, particularly ultraviolet X-rays, gamma rays, they can present a greater risk, but the danger is reduced if the exposure is minimised.

Let's do a check of some of the ideas we just talked about.

Which two of the following statements are true? So you're looking for two of these which are true and the rest are all false.

Pause the video, have a read through, make your decision, off you go.

Right, I'll tell you which ones are true.

A was true, light is a kind of electromagnetic radiation.

Radiation just means something which is emitted and transfers energy.

But the other statement that's true is F, the Sun does emit some harmful radiation.

Radiation is naturally occurring.

Radiation is not always dangerous and harmful.

There is potentially harmful radiation in the countryside, such as ultraviolet from the Sun, for example.

Very, very few electronic devices are going to emit harmful radiation, because if they did, they wouldn't be allowed to be put on sale.

Okay, well done.

Lots of information about different kinds of electromagnetic waves with the different frequencies.

So there are four parts to this task to complete this lesson.

Most of the parts of this task are fairly straightforward, so you should pause the video now and have a go at each part.

Off you go.

Right, well done for your effort on that task.

I'll give you some feedback now.

So, what is meant by the spectrum of electromagnetic waves? It means the full or continuous range of frequencies that electromagnetic waves can have, the spectrum of frequencies that electromagnetic waves have, which is all possible frequencies.

Part two was just adding the names of the seven frequency ranges of electromagnetic waves to the diagram.

Should have gone starting from the lowest frequency electromagnetic waves, that's radio waves, then microwaves, then infrared, then visible light, then ultraviolet, then X-rays, then gamma rays, as shown in this diagram here.

Part three of this task describes some properties that all electromagnetic waves have.

Hopefully you've included some of these.

So all electromagnetic waves consist of oscillations or ripples in electric and magnetic fields, that's what they are.

Electromagnetic waves are transverse waves, and in air or a vacuum, they all travel at the speed of light, 300 million metres per second, three times 10 to the eight metres per second.

And all electromagnetic waves transfer energy.

Well done if you've got most or all of those.

And part four of this task, state the only difference between each kind of electromagnetic wave that causes them to interact differently with different materials.

What we're looking for here is their frequency.

You might have mentioned their wavelength, but really they're defined by their frequency, rather than their wavelength.

Very well done if your answers were along those lines.

Here's a summary of the lesson.

Electromagnetic waves or electromagnetic radiation are transverse oscillations or ripples in electric and magnetic fields.

Light is electromagnetic radiation that we can see.

Colours in the visible spectrum have different frequencies.

Violet light has the highest frequency in the visible spectrum and refracts more than red light because violet light slows down more in glass.

Electromagnetic waves in other frequency ranges interact differently with different materials.

In order of frequency, starting with the lowest frequency, the spectrum of electromagnetic waves is radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

And all electromagnetic waves can transfer energy, and they all travel at the same speed in air.