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What are the main points in this model of matter?

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All matter is made of up particles, these particles behave in different ways whether they are solid, liquid or gas.

Particles in solids are held together very closely.

This makes them very strong and difficult to break apart. Solids can also hold their own shape

The particles don't move around very much but simply vibrate in their spot.

Particles in liquids are quite close to each other, however they can move past each other very easily.

This makes liquids very easy to break apart and why they cannot hold their own shape, but instead take the shape of their container

The particles in liquids move around quite a bit, bumping gently past each other.

Particles in gases move around very quickly with a lot of space between them, this means you can compress them very easily.

Gases don't just take the shape of their container they fill the space of the container that they are in

Solids, liquids and gases can of course change between each other simply by heating or cooling them. The processes involved in changing each states are

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Particle Model of Solids, Liquids and Gases

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All matter is made of up particles, these particles behave in different ways whether they are solid, liquid or gas. Solids Particles in solids are held together very closely. This makes them very strong and difficult to break apart. Solids can also hold their own shape The particles don't move around very much but simply vibrate...

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The Particle Model of Matter Vs The Wave Model

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The Particle Model of Matter Vs The Wave Model

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Find out how the two ideas are linked and explain the relationship in your own words (or use labelled diagrams).

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1. What does the term 'wave' refer to?
2. Identify the three ways that waves transfer energy.
3. Explain what is meant by "Waves transfer energy but not mass".
4. What do the terms 'frequency', 'amplitude' and 'wavelength' refer to, and how these change between different types of waves.

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'Wave' is a common term for a number of different ways in which energy is transferred:

In electromagnetic waves, energy is transferred through vibrations of electric and magnetic fields.

In sound waves, energy is transferred through vibration of air particles or particles of a solid through which the sound travels.

In water waves, energy is transferred through the vibration of the water particles.

Waves transfer energy but not mass

When we watch surf waves coming into shore, it's easy to think that individual water particles are moving towards us, but that's not actually the case. The particles involved in waves move back and forth perpendicularly to the way the wave is going, but don't move significantly in the direction of the wave. The particles 'take part' in the wave by bumping into one another and transferring energy. This is why energy can be transferred, even though the average position of the particles doesn't change.

How does this work? It can help to think of a buoy bobbing in the ocean. The buoy is moved up and down by the waves that pass by it, but doesn't move directionally across the water.

You could also think about a Mexican wave at a sports match. The wave moves around the arena, but the audience members don't move around with it - they only stand up and sit down (a perpendicular movement to the wave direction).

Particles in a water wave exchange kinetic energy for potential energy

When particles in water become part of a wave, they start to move up or down. This means that kinetic energy (energy of movement) has been transferred to them. As the particles move further away from their normal position (up towards the wave crest or down towards the trough), they slow down. This means that some of their kinetic energy has been converted into potential energy - the energy of particles in a wave oscillates between kinetic and potential energy.

Thinking about potential energy can help us understand why tsunamis can be so damaging. When a tsunami approaches the shore, it shoals (becomes much higher), so the water particles are displaced further from equilibrium. They acquire a lot of potential energy, and this is released when the wave interacts with land.

Measuring the energy in a wave

Why do some waves have more energy than others? A wave's frequency and wavelength are both indicators of its energy, but this differs for different types for waves.

For water waves, those with a high speed and long wavelength (like a tsunami) have the most energy. For electromagnetic waves, speed is constant, so waves with a high frequency and a short wavelength (like X-rays) are the most energetic.

For all waves, a greater amplitude means more energy.

In the electromagnetic spectrum interactive you can click on various wavelengths to learn more about the waves that make up the spectrum.

Harnessing wave energy

Scientists in New Zealand and elsewhere are looking at how to turn the energy of water waves into electricity. The oceans around New Zealand are promising places to generate wave power because we have large waves and strong currents. Generating wave power would involve an underwater device (like a paddle, for example) that would move in response to waves and drive a turbine that would produce electricity.

The idea of wave power is appealing because waves are a sustainable resource - they can't be used up (unlike other resources, like coal, that are used for making electricity in New Zealand). However, they are quite inefficient - they need a lot of coastal space to generate useful quantities of energy. Using mathematical modelling and physical model building, Kiwi scientists are investigating how to harness wave power, but it will be some time before we're using electricity from wave power in our homes.

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'Wave' is a common term for a number of different ways in which energy is transferred: In electromagnetic waves, energy is transferred through vibrations of electric and magnetic fields. In sound waves, energy is transferred through vibration of air particles or particles of a solid through which the sound travels.

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Copy the following diagram under the heading above.

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1. Explain how sound energy moves.
2. Outline how sound and light energy is similar and different.
3. What type of wave is a sound wave? Draw a labelled diagram showing how a sound wave differs from a light wave. What do rarefractions and compressions refer to?
4. What does diffraction refer to, in terms of sound energy?
5. Explain how a whispering gallery works.
6. Copy the diagram of the four waves from the "Understanding Amplitude & Frequency" and explain what each waves is showing in terms of what the wave sounds like.
7. What is the speed of sound? How does a sonic boom occur?
8. Describe how fast sound waves travel through different materials, particularly gases, liquids and solids. How does the temperature of these materials affect the speed of sound?

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by Chris Woodford. Last updated: February 20, 2018.

Sound-it's almost impossible to imagine a world without it. It's probably the first thing you experience when you wake up in the morning-when you hear birds chirping or your alarm clock bleeping away. Sound fills our days with excitement and meaning, when people talk to us, when we listen to music, or when we hear interesting programs on the radio and TV. Sound may be the last thing you hear at night as well when you listen to your heartbeat and drift gradually into the soundless world of sleep. Sound is fascinating-let's take a closer look at how it works!

Photo: Sound is energy we hear made by things that vibrate. Photo by William R. Goodwin courtesy of US Navy.

What is sound?

Sound is the energy things produce when they vibrate (move back and forth quickly). If you bang a drum, you make the tight skin vibrate at very high speed (it's so fast that you can't usually see it), forcing the air all around it to vibrate as well. As the air moves, it carries energy out from the drum in all directions. Eventually, even the air inside your ears starts vibrating-and that's when you begin to perceive the vibrating drum as a sound. In short, there are two different aspects to sound: there's a physical process that produces sound energy to start with and sends it shooting through the air, and there's a separate psychological process that happens inside our ears and brains, which convert the incoming sound energy into sensations we interpret as noises, speech, and music. We're just going to concentrate on the physical aspects of sound in this article.

Sound is like light in some ways: it travels out from a definite source (such as an instrument or a noisy machine), just as light travels out from the Sun or a light bulb. But there are some very important differences between light and sound as well. We know light can travel through a vacuum because sunlight has to race through the vacuum of space to reach us on Earth. Sound, however, cannot travel through a vacuum: it always has to have something to travel through (known as a medium), such as air, water, glass, or metal.

Robert Boyle's classic experiment

The first person to discover that sound needs a medium was a brilliant English scientist known as Robert Boyle (1627-1691). He carried out a classic experiment that you've probably done yourself in school: he set an alarm clock ringing, placed it inside a large glass jar, and while the clock was still ringing, sucked all the air out with a pump. As the air gradually disappeared, the sound died out because there was nothing left in the jar for it to travel through.

Artwork: Robert Boyle's famous experiment with an alarm clock.

1. Put a ringing alarm clock inside a large glass case with a valve on top. Close the valve so no air can get in.

2. You can easily hear the clock ringing because the sound travels through the air in the case and the glass, before continuing to your ears.

3. Switch on the vacuum pump and remove the air from the case. As the case empties, the ringing clock sounds fainter and fainter until you can barely hear it at all. With little or no air in the case, there's nothing to carry the sound to your ears.

4. Switch off the pump. With the clock still ringing, open the valve on top of the case. As air rushes back in, you'll hear the clock ringing once again. Why? Because with air once again inside the case, there's a medium to carry the sound waves from the ringing clock to your ears.

How sound travels

When you hear an alarm clock ringing, you're listening to energy making a journey. It sets off from somewhere inside the clock, travels through the air, and arrives some time later in your ears. It's a little bit like waves traveling over the sea: they start out from a place where the wind is blowing on the water (the original source of the energy, like the bell or buzzer inside your alarm clock), travel over the ocean surface (that's the medium that allows the waves to travel), and eventually wash up on the beach (similar to sounds entering your ears). If you want to learn more about how sea waves travel, read our article on surfing science.

Artwork: Sound waves and ocean waves compared. Top: Sound waves are longitudinal waves: the air moves back and forth along the same line as the wave travels, making alternate patterns of compressions and rarefactions. Bottom: Ocean waves are transverse waves: the water moves back and forth at right angles to the line in which the wave travels.

There is one crucially important difference between waves bumping over the sea and the sound waves that reach our ears. Sea waves travel as up-and-down vibrations: the water moves up and down (without really moving anywhere) as the energy in the wave travels forward. Waves like this are called transverse waves. That just means the water vibrates at right angles to the direction in which the wave travels. Sound waves work in a completely different way. As a sound wave moves forward, it makes the air bunch together in some places and spread out in others. This creates an alternating pattern of squashed-together areas (known as compressions) and stretched-out areas (known as a rarefactions). In other words, sound pushes and pulls the air back and forth where water shakes it up and down. Water waves shake energy over the surface of the sea, while sound waves thump energy through the body of the air. Sound waves are compression waves. They're also called longitudinal waves because the air vibrates along the same direction as the wave travels.

To get the difference between transverse and longitudinal waves clear in your mind, take a look at these two little animations on Wikimedia Commons:

The science of sound waves

If you've ever got time on your hands while you're lazing on the beach, try watching the different ways in which waves can behave. You'll notice that waves traveling on water can do all kinds of clever things, like smashing into a wall and reflecting straight back with more or less the same intensity. They can also spread out in ripples, creep their way up the beach, and do other clever stuff. What's happening here with water waves doesn't actually have anything to do with the water: it's simply the way energy behaves when it's carried along by waves. Similar things happen with other kinds of waves-with light and with sound too.

You can reflect a sound wave off something the same way light will reflect off a mirror or water waves will bounce off a sea wall and go back out to sea. Stand some distance from a large flat wall and clap your hands repeatedly. Almost immediately you'll hear a ghostly repeat of your clapping, slightly out of step with it. What you hear is, of course, sound reflection, better known as an echo: it's the sound energy in your clap traveling out to the wall, bouncing back, and eventually entering your ears. There's a delay between the sound and the echo because it takes time for the sound to race to the wall and back (the bigger the distance, the longer the delay).

Picture: Reflected sound is extremely useful for "seeing" underwater where light doesn't really travel-that's the basic idea behind sonar. Here's a side-scan sonar (reflected sound) image of a World War II boat wrecked on the seabed. Photo courtesy of U.S. National Oceanographic and Atmospheric Administration and US Navy.

Sound waves lose energy as they travel. That's why we can only hear things so far and why sounds travel less well on blustery days (when the wind dissipates their energy) than on calm ones. Much the same thing happens on the oceans. Crisp water waves can sometimes travel vast distances across the ocean, but they can also be messed up when squally weather dissipates their energy over shorter distances.

Sound waves are like light and water waves in other ways too. When water waves traveling long distances across the ocean flow around a headland or into a bay, they spread out in circles like ripples. Sound waves do exactly the same thing, which is why we can hear around corners. Imagine you're sitting in a room off a corridor and, much further up the corridor, there's an identical room where someone is practicing a trumpet inside. Sound waves travel out from the trumpet, spreading out as they go. They ripple out down the corridor, race along it, ripple through the doorway into your room and eventually reach your ears. The tendency waves have to spread out as they travel and bend around corners is called diffraction.

Whispering galleries and amphitheaters

You might not think you could hear someone whispering if they sat a long way away, but if they can make the sound of their voice bounce off something into your ears, their voice will travel much further than usual.

If you're inside a building with a giant dome, the sounds you make will reflect off the curved roof like light rays bouncing off a mirror. Buildings that work this way are sometimes called whispering galleries. The dome of the US Capitol and the famous reading room in the British Museum in London are two well known examples. You can hear the same effect at work outside when you sit in a naturally curved area called an amphitheater. You can talk in a normal voice and still be heard very clearly a considerable distance away.

Photos: 1) The Capitol in Washington, DC has a whispering gallery inside its dome. Photo by courtesy of The Architect of the Capitol. 2) It's easy to hear people talking in this amphitheater in Iraq. Photo by Jason L. Andrade courtesy of US Marine Corps.

Measuring waves

All sound waves are the same: they travel through a medium by making atoms or molecules shake back and forth. But all sound waves are different too. There are loud sounds and quiet sounds, high-pitched squeaks and low-pitched rumbles, and even two instruments playing exactly the same musical note will produce sound waves that are quite different. So what's going on?

The energy something makes when it vibrates produces sound waves that have a definite pattern. Each wave can be big or small: big sound waves have what's called a high amplitude or intensity and we hear them as louder sounds. Loud sounds are equivalent to larger waves moving over the sea (except that, as you'll remember from up above, the air is moving back and forth, not up and down as the water does).

Apart from amplitude, another thing worth noting about sound waves is their pitch, also called their frequency. Soprano singers make sound waves with a high pitch, while bass singers make waves with a much lower pitch. The frequency is simply the number of waves something produces in one second. So a soprano singer produces more energy waves in one second than a bass singer and a violin makes more than a double bass.

Understanding amplitude and frequency

This artwork shows four waves that would sound different. If you're using a fairly up-to-date web browser, you can compare how they sound by playing the samples below. (If you don't see the sound clips, please try a different browser.)

1. The top wave represents a typical sound wave vibrating at a certain amplitude (its height) and frequency (how many peaks and troughs there are in a certain amount of time).
Your browser does not support the audio element.

2. This wave has the same frequency as the first wave (the same number of peaks and troughs) but twice the amplitude (it's twice as high). A sound wave like this would sound louder than the first wave but the same pitch.
Your browser does not support the audio element.

3. This wave has half the frequency of the second wave (half the number of peaks and troughs) but the same amplitude (it's exactly the same height). A sound wave like this would sound deeper (lower pitched) than the second wave, about as loud as the second wave, and louder than the first wave.
Your browser does not support the audio element.

4. This wave has twice the frequency of waves 1 and 2 and four times the frequency of wave 3, so it would sound much higher in pitch than the other waves. It has the same amplitude as waves 2 and 3, so it would sound just about as loud.
Your browser does not support the audio element.

Remember, however, that sound waves don't look like this as they travel. These up-and-down patterns are what you'll see if you study sound wave signals with an oscilloscope (a kind of electronic graph-drawing machine). Sound waves travel through the air as squashed-up compressions and stretched-out rarefactions. They only look like this on an oscilloscope trace.
Why instruments sound different

But here's a conundrum. If a violin and a piano make sound waves with the same amplitude and frequency, how come they sound so different? If the waves are identical, why don't the two instruments sound exactly the same? The answer is that the waves aren't identical! An instrument (or a human voice, for that matter) produces a whole mixture of different waves at the same time. There's a basic wave with a certain amplitude and pitch, called the fundamental, and on top of that there are lots of higher-pitched sounds called harmonics or overtones. Each harmonic has a frequency that's exactly two, three, four, or however many times higher than the fundamental. Every instrument produces a unique pattern of a fundamental frequency and harmonics, called timbre (or sound quality). All these waves add together to give a unique shape to the sound wave produced by different instruments, and that's one reason why they sound different. The other reason is that the amplitude of the waves made by a particular instrument changes in a unique way as the seconds tick by. Flute sounds are immediate and die quickly, while piano sounds take longer to build up and die out more slowly as well. You'll find a much longer explanation of this in our article about electronic music synthesizers.

The speed of sound

When we talk about the speed of sound, what exactly do we mean? Now you know that sound carries energy in a pattern of waves, you can see that the speed of sound means the speed at which the waves move-the speed at which the energy travels between two places. When we say that a jet airplane "breaks through the sound barrier," we mean that it accelerates so fast that it overtakes the incredibly high-intensity (that is, noisy) sound waves its engines are making, producing a horrible noise called a sonic boom in the process. That's why you'll see a fighter plane whizz overhead a second or two before you hear the vicious scream of its jet engines.

Photo: Breaking through the sound barrier creates a sonic boom. The mist you can see, which is called a condensation cloud, isn't necessarily caused by an aircraft flying supersonic: it can occur at lower speeds too. It happens because moist air condenses due to the shock waves created by the plane. You might expect the plane to compress the air as it slices through. But the shock waves it generates alternately expand and contract the air, producing both compressions and rarefactions. The rarefactions cause very low pressure and it's these that make moisture in the air condense, producing the cloud you see here. Photo by John Gay courtesy of US Navy.

The speed of sound in air (at sea level) is about 1220 km/h (760 mph or 340 meters per second). Compared to light waves, sound waves creep along at a snail's pace-about a million times slower. You see lightning much sooner than you hear it because the light waves reach you pretty much instantly, while the sound waves take about 5 seconds to cover each 1.6 km (1 mile).

One thing to note about the speed of sound is that there's really no such thing! Sound travels at different speeds in solids, liquids, and gases and even its speed in one material can change. Very roughly speaking, how fast it goes varies according to the density of the medium (how much stuff there is there). It's faster in solids than in liquids and faster in liquids than in gases: for example, sound travels about 15 times faster in steel than in air, and about four times faster in water than in air.That's why whales use sound to communicate over such long distances and why submarines use SONAR (sound navigation and ranging; a sound-based navigation system similar to radar only using sound waves instead of radio waves). It's also one of the reasons why it's very hard to figure out where the noise of a boat engine is coming from if you're swimming in the sea. (Note: The way sound travels through different materials is much more complex than this. A good explanation of why sound goes so fast in solids would mean I'd have to introduce a concept called phonons-and I'm going to skip that in this simple, introductory article, gloss over the complexities, and "pretend" that density is what makes the difference.)

Sound travels at different speeds in different gases-and can go at different speeds even in the same gas. It travels much faster in warm air near the ground than in colder air higher up, for example. And it travels roughly three times faster in helium gas than in ordinary air, because helium is much less dense. That's why people who breathe in helium talk in funny voices: the sound waves their voices make travel faster-with higher frequency.

Sound in practice

Photo: Musical sound is arguably humankind's greatest invention. This superb Steinway grand piano dates from 1876 and sits in the amazing gallery at the National Trust's Lanhydrock country house in Cornwall, England.

Sound is a hugely important part of life on Earth. Most animals listen out for noises-things that signal the possibility of eating or being eaten. Many creatures also exchange meaningful sounds, either to communicate with members of the same species or warn off predators and rivals. Humans have evolved this ability into spoken language (as a way of exchanging information) and music (essentially, a sound-based system for communicating emotion).

We've also developed a variety of different sound technologies. We've invented musical instruments that can make a huge range of different musical sounds, from simple drums and percussion instruments to sophisticated electronic synthesizers that can generate any sound you care to imagine. We can record sounds on such things as compact discs or with newer technologies like MP3 (sound files stored in highly compressed forms on computers). We can also use very high frequency sounds, known as ultrasound, for everything from cleaning false teeth to studying the development of a baby inside a mother's womb. We've even taught computers to listen to our spoken words and turn them into written language using voice recognition software-appropriately enough, that's how I wrote this article for you today!

Find out more

On this website

On other sites

Explore Sound: A comprehensive educational site from the Acoustical Society of America, with activities for students of all ages.

Sounds Amazing: A great collection of interactive science lessons from the University of Salford, which explains what sound waves are and the different ways in which they behave.

Books

Educational books for younger readers

Sound by Angela Royston. Raintree, 2017. A basic introduction to sound and musical sounds, including simple activities. Ages 7-9.

Sound (Science in a Flash) by Georgia Amson-Bradshaw. Franklin Watts/Hachette, 2017. Simple facts, experiments, and quizzes fill this book; the visually exciting design will appeal to reluctant readers. Also for ages 7-9.

Experimenting with Sound Science Projects by Robert Gardner. Enslow Publishers, 2013. A comprehensive 120-page introduction, running through the science of sound in some detail, with plenty of hands-on projects and activities (including welcome coverage of how to run controlled experiments using the scientific method). Ages 9-12.

Cool Science: Experiments with Sound and Hearing by Chris Woodford. Gareth Stevens Inc, 2010. One of my own books, this is a short introduction to sound through practical activities, for ages 9-12.

Popular science

Academic books

Master Handbook of Acoustics by F. Alton Everest and Ken Pohlmann. McGraw-Hill Education, 2015. A comprehensive reference for undergraduates and sound-design professionals.

The Science of Sound by Thomas D. Rossing, Paul A. Wheeler, and F. Richard Moore. Pearson, 2013. One of the most popular general undergraduate texts.

More to explore on our website...

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Sound - The science of waves, how they travel, how we use them

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by Chris Woodford. Last updated: February 20, 2018. Sound-it's almost impossible to imagine a world without it. It's probably the first thing you experience when you wake up in the morning-when you hear birds chirping or your alarm clock bleeping away.

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Print off a copy of the EMS diagram

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Introduction to electromagnetic waves

Electromagnetic radiation is one of the many ways that energy travels through space. The heat from a burning fire, the light from the sun, the X-rays used by your doctor, as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation. While these forms of energy might seem quite different from one another, they are related in that they all exhibit wavelike properties.

While it's good to have a basic understanding of what electromagnetic radiation is, most chemists are less interested in the physics behind this type of energy, and are far more interested in how these waves interact with matter. More specifically, chemists study how different forms of electromagnetic radiation interact with atoms and molecules. From these interactions, a chemist can get information about a molecule's structure, as well as the types of chemical bonds it contains. Before we talk about that, however, it's necessary to talk a little bit more about the physical properties of light waves.

Basic properties of waves: Amplitude, wavelength, and frequency

As you might already know, a wave has a trough (lowest point) and a crest (highest point). The vertical distance between the tip of a crest and the wave's central axis is known as its amplitude. This is the property associated with the brightness, or intensity, of the wave. The horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave. These lengths can be visualized as follows:

Keep in mind that some waves (including electromagnetic waves) also oscillate in space, and therefore they are oscillating at a given position as time passes. The quantity known as the wave's frequency refers to the number of full wavelengths that pass by a given point in space every second; the SI unit for frequency is Hertz , which is equivalent to "per seconds" written as or . As you might imagine, wavelength and frequency are inversely proportional: that is, the shorter the wavelength, the higher the frequency, and vice versa. This relationship is given by the following equation:

To illustrate the relationship between frequency and wavelength, let's consider an example.

Example: Calculating the wavelength of a light wave

We can start with our equation that relates frequency, wavelength, and the speed of light.

Next, we rearrange the equation to solve for wavelength.

Lastly, we plug in our given values and solve.

Now that we have an understanding of some basic properties of waves, we'll look at the different types of electromagnetic radiation.

The electromagnetic spectrum

Electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies; this classification is known as the electromagnetic spectrum. The following table shows us this spectrum, which consists of all the types of electromagnetic radiation that exist in our universe.

As we can see, the visible spectrum-that is, light that we can see with our eyes-makes up only a small fraction of the different types of radiation that exist. To the right of the visible spectrum, we find the types of energy that are lower in frequency (and thus longer in wavelength) than visible light. These types of energy include infrared (IR) rays (heat waves given off by thermal bodies), microwaves, and radio waves. These types of radiation surround us constantly, and are not harmful, because their frequencies are so low. As we will see in the section, "the photon," lower frequency waves are lower in energy, and thus are not dangerous to our health.

To the left of the visible spectrum, we have ultraviolet (UV) rays, X-rays, and gamma rays. These types of radiation are harmful to living organisms, due to their extremely high frequencies (and thus, high energies). It is for this reason that we wear suntan lotion at the beach (to block the UV rays from the sun) and why an X-ray technician will place a lead shield over us, in order to prevent the X-rays from penetrating anything other than the area of our body being imaged. Gamma rays, being the highest in frequency and energy, are the most damaging. Luckily though, our atmosphere absorbs gamma rays from outer space, thereby protecting us from harm.

Next, we will talk about the relationship between a wave's frequency and its energy.

Quantization of energy and the dual nature of light

Planck's discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave. In actuality, light seemed to have both wavelike and particle-like properties.

Planck's discoveries paved the way for the discovery of the photon. A photon is the elementary particle, or quantum, of light. As we will soon see, photons can be absorbed or emitted by atoms and molecules. When a photon is absorbed, its energy is transferred to that atom or molecule. Because energy is quantized, the photon's entire energy is transferred (remember that we cannot transfer fractions of quanta, which are the smallest possible individual "energy packets"). The reverse of this process is also true. When an atom or molecule loses energy, it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule. This change in energy is directly proportional to the frequency of photon emitted or absorbed. This relationship is given by Planck's famous equation:

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Light: Electromagnetic waves, the electromagnetic spectrum and photons (article) | Khan Academy

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Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

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Make a note of any VIP's in your classbook.

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This revision bite includes the following subject areas: electromagnetic spectrums, the main parts of radio and television receivers.

Work through them all or go to the ones that interest you. You may wish to print a hard copy for your reference.

You need to know that there exists a large family of waves, each with a different wavelength range, called the electromagnetic spectrum (sometimes shortened to the e-m spectrum). These waves all travel at the speed of light (300,000,000 metres per second) in a vacuum.

In addition, for Credit Level only, you need to know more about these waves - what the waves are, what they have in common, what is special about each part of the spectrum and what the waves are used for.

The electromagnetic spectrum

Electromagnetic waves carry transverse vibrations in electrical and magnetic fields, not vibrating particles.

Electromagnetic waves do not need matter to travel through - they can travel through empty space (a vacuum).

In a vacuum, all electromagnetic waves travel at approximately 3 x 10⁸ m/s - the fastest speed possible.

When electromagnetic waves travel through matter (for example, light through air or glass), they travel a bit slower than this but rarely less than half as fast as in a vacuum. The value for light travelling through an optical fibre, for example, is taken as 2 x 10⁸ m/s.

The table below demonstrates the electromagnetic spectrum. You may want to print this table out as a permanent summary.

The electromagnetic spectrum ranges from long, low frequency waves (like radio waves which can be used for communication) to short, high frequency waves (like gamma rays which can be used for medical treatment).

Listen to the audio clip to learn about the basis of radiation.

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BBC - Standard Grade Bitesize Physics - Using the spectrum : Revision

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This revision bite includes the following subject areas: electromagnetic spectrums, the main parts of radio and television receivers. Work through them all or go to the ones that interest you. You may wish to print a hard copy for your reference.

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This prezi has been prepared by a student, but the information appears correct - double check with a google search of the facts if you feel some points might be inaccurate. Note down the main or important properties of each member of the EMS. Identify where each wave is used in our lives.

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PROPERTIES AND USES OF ELECTROMAGNETIC SPECTRUM

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PROPERTIES AND USES OF ELECTROMAGNETIC SPECTRUM Visible lights Properties Visible lights are the most common electromagnetic radiation which can be detected by the eye Visible lights waves are given off by any hot glowing bodies such as lightbulbs and the sun.

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Straw Flute

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Information about Create a straw flute with Fizzics Education | Kids Science Experiments

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Science lesson resources for kids from Preschool and Secondary school. Make science fun with Fizzics

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Coathanger Gong

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Information about Coathanger gong experiment with Fizzics Education | Kids Science Experiments

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Science lesson resources for kids from Preschool and Secondary school. Make science fun with Fizzics

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Star Wars Sound Effects

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Information about Slinky Star Wars Sounds with Fizzics Education | Kids Science Experiments

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Science lesson resources for kids from Preschool and Secondary school. Make science fun with Fizzics

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Pick a few activities from this webpage to try.

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Bernard and Barbro Osher West Gallery 1: Human Phenomena

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Report on your results. It can be via labelled diagrams or a recount.

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The Optical Society: Exploring the Science of Light | Optics For Kids

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The Optical Society presents Exploring the Science of Light

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Draw labelled diagrams showing your results.

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This water refraction science experiment has such a "wow factor" and is so quick and easy I can't believe my kids and I haven't done it before. It would fit right in with our DIY science camp series, too. Best of all, there is almost no set up, but once I showed it to the kids, they experimented on their own and debated the reasons for the results. You have the option of setting up the science experiment as we did, or doing it right now with the glass of water sitting next to you!

Water Refraction Science Experiment
What you need:

Water

Jar or glass

A paper with a design on it. If you wish, you can download and print our printable. It is two pages and includes the colored bars and two arrows facing the same direction.

Instructions:
Place a jar or glass about 6 inches in front of the colored bars or arrows. Pour in the water. What happens?

Watch the video!
To make it more fun:
Ask your kids to keep their eyes on the bars/arrows as you slowly pour the water into the jar.

I told my kids I had a magic liquid. I'm pretty sure my 6 year old believed me, but my 10 year old unconvincingly said, "It's water, mom." But then after I performed the experiment, he said, "Now try it with water." Ha! So I guess I did fool him.
Explorations:

Does it make a difference how close the water is to the paper?

Does it make a difference if the jar is square or round? What about the size of the jar or glass?

Draw a diagram of what you think is happening to the light rays. (See explanation below)

Super nerdy kids (I say that with love) can learn more about refraction of light here.

The science behind the water refraction experiment:
Refraction is the bending of light. In this case, light traveled from the air, through the front of the glass jar, through the water, through the back of the glass jar, and then back through the air, before hitting the picture. Whenever light passes from one medium into another, it refracts.

In addition, the water acts as a magnifying glass, which bends the light toward the center. The light comes together at the focal point and beyond the focal point the image looks reversed because the light that was on the right is now on the left, and vice versa. Clear as mud? ( Note: I am not a science teacher and if you would like to correct or add to my explanation in the comments, I welcome it!)

Want another cool and magical water experiment? Find out how to make a coin jump from a bottle. Or find more fun indoor water activities for kids.

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Magic Happens When You Pour Water Into A Jar

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This water refraction science experiment has such a 'wow factor' and is so quick and easy I can't believe my kids and I haven't done it before. It would fit right in with our DIY science camp series, too.

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There are a few experiments relating to the reflection of light on this webpage - you can have a go at each of them or just pick a couple. Make sure that you report on whatever you choose to do.

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Practical Physics " Light and optics " Reflection of light

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Report on what you did - via labelled diagrams or a recount.

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Invisible convection currents are revealed using a very colorful demonstration.
Cool, crisp, clean mountain air has long been an important reason why people move to Colorado, USA. Unfortunately, the air in the city of Denver isn't quite as clean as it has been. By the 1970s, pollution over the city had a name-the "brown cloud." Denver's location at the foot of the Rocky Mountains makes it prone to temperature inversions in which warm air higher in the atmosphere traps cooler air near the ground. This condition prevents pollutants from escaping into the atmosphere. However, the phenomenon of temperature inversion is not unique to Denver, as evidenced by numerous reports of similar brown cloud sightings over major cities throughout the world. This demonstration provides a great illustration of what's really happening in the atmosphere as hot and cold air masses meet.

SICK Science ® is a registered trademark of Steve Spangler, Inc. All Rights Reserved.

Experiment Materials

Four empty, identical bottles (Browse the juice aisle at a grocery store to find bottles similar to those shown. As a general rule, the opening of the bottle should be at least an inch [25 mm] in diameter.)

Access to hot and cold water

Coloring Tablets or Food Coloring

3 x 5 inch (8 x 13 cm) card or an old playing card

Masking tape

Pen

Paper towels

Adult supervision

Experiment

How Does It Work

Hot air balloons rise because warm air in a balloon is lighter and less dense than cold air. Similarly, warm water is lighter or less dense than cold water. When the bottle of warm water is placed on top of the cold water, the more dense cold water stays in the bottom bottle and the less dense warm water is confined to the top bottle. However, when the cold water bottle sits on top of the warm water bottle, the less dense warm water rises into the top bottle and the cold water sinks into the bottom bottle. The movement of the water is clearly seen as the yellow and blue food colorings mix, creating a green liquid.

The movement of the warm and cold water inside the bottles is referred to as a convection current. In our daily life, warm currents of water occur in oceans. The warm Gulf Stream moves northward along the American Eastern Seaboard and crosses the Atlantic Ocean all the way to Europe. Convection currents in the atmosphere are responsible for the formation of thunderstorms as warm and cold air masses collide.

Although the colored liquids that mix are more interesting to watch, the other set of warm and cold water bottles helps to illustrate an important phenomenon that can occur in the atmosphere in cooler months. During daylight hours, the Sun heats the surface of the Earth and the layer of air closest to the Earth warms. This warm air rises and mixes with other atmospheric gases. When the Sun goes down, less dense warm air higher in the atmosphere blankets the colder air closer to the surface. Because the colder air is more dense than the warm air, the colder air is trapped close to the Earth and the atmospheric gases do not mix. This is referred to as a temperature inversion.

Take It Further

You can take this activity to the next level with a cool demonstration using the Split Demo Tank! Fill one side of the tank with cold (blue) water, and the other side with hot (yellow) water. Remove the divider between the tanks and the water swirls together. As things calm down in the tank, the hot water ends up on top and traps the cold water underneath it. You can use a spoon to stir the two liquids together. To stir up things in the atmosphere, you'll need a pretty good wind or even a storm.

Real-World Application

What are the results of a temperature inversion in the atmosphere? Air pollution is much more noticeable during a temperature inversion since pollutants such as car exhaust and particulates are trapped in the layer of cool air close to the surface. As a result, state agencies in many parts of the country oxygenate automobile fuels during winter months with additives like MTBE in an attempt to reduce the harmful effects of trapped pollution. It is this trapped pollution that causes the brown cloud effect. Wind or precipitation can often alleviate the brown cloud by stirring and breaking up the layer of warm air that traps the cold air and pollution near the surface of the Earth.

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Colorful Convection Currents | Experiments | Steve Spangler Science

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Invisible convection currents are revealed using a very colorful demonstration. Cool, crisp, clean mountain air has long been an important reason why people move to Colorado, USA. Unfortunately, the air in the city of Denver isn't quite as clean as it has been. By the 1970s, pollution over the city had a name-the "brown cloud."

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Print out the table and paste it into your classbook.

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Applications of Absorption, Reflection and Refraction in Everyday Situations

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Applications of Absorption, Reflection and Refraction in Everyday Situations

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You should be able to state what absorption, reflection and refraction of light energy means by this point. Using what you know about each property of light, plus more research if you need to, come up with a list of 3-5 practical applications or uses for each property of light, in common/everyday situations. You should include diagrams or photo's of your applications.

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Find definitions, in a physics context, for the following terms:
* Motion
* Velocity
* Speed
* Force
* Mass
* Acceleration
* Newton
* Displacement
* Vector

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Use the relationships identified above to solve the problems attached. Make sure you show all working out, from writing the appropriate equation, working through each step to the answer.

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* Use an equation to describe the relationship between force, mass and acceleration.
* Use an equation to describe the relationship between speed, distance and time.

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State Newton's Third Law, and draw diagrams to represent the main ideas of the law.

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This task has been assigned to you on Education Perfect. There are instructions and a results table to copy or print out. Write a prac report in your book for the activity - Aim through to Conclusion.

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State Newton's First Law, and draw diagrams to represent the main ideas of the law.

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This task has been assigned to you on Education Perfect. There are instructions and a results table to copy or print out. Write a prac report in your book for the activity - Aim through to Conclusion.

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State Newton's Second Law, and draw diagrams to represent the main ideas of the law.

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This task has been assigned to you on Education Perfect. There are instructions and a results table to copy out or print out. Write a prac report in your book for the activity - Aim through to Conclusion.