What Are Some Properties of Waves? · 2020-03-13 · Sound waves also have these three properties....

Level A reading coming soon.

What Are Some Properties of Waves?

ScienceVocabulary

amplitude

dependent

frequency

independent

wavelength

This image represents the crests and troughs of a wave. You will learnabout three properties of waves that are related to a wave's crests and

W H A T A R E S O M E P R O P E R...

2020 Teachers' Curriculum Institute Level: A

troughs. Each of these three properties tells you something differentabout a wave. Recognizing patterns in these properties helps youdescribe and compare waves.

1. The Properties of WaterWavesThink about being in a swimming pool on a warm summer day. Thewater is cold, so you step into it slowly. Your friend has a different idea.He jumps into the pool. SPLASH! The waves that you make are small.But the waves that your friend makes are much larger.

The Amplitude of Water Waves

Amplitude is the largestdistance that matter in awave moves from its restposition. A wave’s amplitudedescribes its height.

The water waves that you and your friend made are both water waves,but different. One of the ways you can tell these waves apart is by theiramplitude. A wave's amplitude describes how big the wave is.

Amplitude is the largest distance that matter moves from its restposition. In water waves, the rest position is midway between the crestof the wave and the trough of the wave. The amplitude of a water waveis the distance from its rest position to its crest. The distance from therest position to the trough is also the amplitude of the wave. Matterreturns to its rest position after a wave has passed through it.

When you and your friend jumped into the pool, the waves you causedhad different patterns. When you stepped in, the waves had a smallamplitude. When your friend jumped in, the waves had a large


Level: A 2020 Teachers' Curriculum Institute

amplitude.

The Wavelength of Water Waves

The crests and troughs of a water wave can also be used to measureanother property called wavelength. Wavelength is how stretched outa wave looks. It is the distance between one crest and the next crest ina wave. The distance between a trough and the next trough in a waveis also wavelength. These distances are the same. If the crests of awater wave are close together, the wave has a short wavelength. If thecrests are far apart, the wave has a long wavelength.

Water waves can have very different wavelengths. The wavelength of awave in a pool might be one meter long. In a sink, the wavelengthmight only be a few centimeters long. The crests are farther apart inthe wave in the pool than the wave in a sink. The water wave in the poolhas a longer wavelength and the water wave in the sink has a shorterwavelength.

Wavelength describes how long a wave is. If a wave’s crests or troughsare close together, the wave has a short wavelength. If they are farapart, the wave has a long wavelength.

The Frequency of Water Waves

Water waves have a third property called frequency. Frequency is howoften a crest passes a certain point in a certain amount of time. Thefrequency of a wave depends on its wavelength and on how fast thewave moves. You can count crests to measure the frequency. Forexample, you could count how many crests pass you in one minutewhile you stand in the shallow part of a pool. If 12 crests pass you, thenthe frequency would be 12 crests per minute.



2. The Properties of Waves on aStringAs you have learned, waves on a string are repeating patterns of crestsand troughs, just like water waves. So, the properties of waves on astring are very similar to the properties of water waves.

Amplitude of Waves on a String

To measure the amplitude ofa wave on a string, measurethe distance from one crestor trough to the wave’s restposition. This distance is thewave’s amplitude.

Just like a water wave, the amplitude of a wave on a string describesthe size of the wave. Picture a jump rope lying on the ground in astraight line. It is at its rest position. You can draw a line with chalkalong the rope to see where the rest position is. Then you take one endof the rope and shake it side to side, creating a wave. The amplitude ofthe wave is the distance from the wave's rest position to its crest. Theamplitude is also the distance from its rest position to its troughbecause these two distances are the same.

You can shake the rope using your whole arm by swinging your armside to side as far as you can. You reach as far as you can to the left,then as far as you can to the right. You make very big waves that havea large amplitude.

You can also shake the rope using just your wrist. You keep your wholearm still and shake only your hand side to side. You make very smallwaves. These waves have a small amplitude.



Wavelength of Waves on a String

In a water wave, the wavelength is the distance between the crests ofthe wave. In a wave on a string, the wavelength is also the distancebetween the crests of the wave. The distance between the troughs ofthe wave is also the wavelength.

You can make waves of different wavelengths in a jump rope. You canshake your hand very quickly side to side. The crests and troughs areclose together, so the wave has a short wavelength. You can shake yourhand side to side very slowly. The crests and troughs are far apart, sothe wave has a long wavelength.

For all waves, wavelength and amplitude are independent of eachother. Two things are independent if they do not affect each other. So,a wave with a large amplitude can have a short or a long wavelength. Awave with a small amplitude can also have a short or long wavelength.

The distance between a wave’s crests or troughs is the wavelength.These distances are the same.

Frequency of Waves on a String

Waves on a string also have frequency. Think about shaking a jumprope. You could draw a mark on the sidewalk that is next to the middleof the jump rope. Then you could shake the rope and count how manycrests pass the mark in a minute. That number per minute is thefrequency of the wave.



3. The Properties of SoundWavesYou have learned that water waves and waves on a string both haveamplitude, wavelength, and frequency. Sound waves also have thesethree properties.

Amplitude of Sound Waves

Like the other types of waves, the amplitude of sound waves is the sizeof the waves. But crests and troughs in sound waves are different fromthose in the other types of waves. Recall that the crests and troughs insound waves are the areas where the matter pushes together andspreads out. The amplitude of sound waves is how much the matterpushes together at the crests and how much it spreads out at thetroughs. If the matter pushes together a lot, the waves have a largeamplitude. If the matter does not push together much, the waves havea small amplitude.

This student is playing atrumpet loudly. Do you thinkthat the amplitude of thesound waves from thetrumpet is large or small?

Sound waves move through air. They are hard to see since you cannotsee air. But you can hear sound waves! So, you measure the propertiesof sound waves by how they sound.

Sound waves with large amplitudes are loud. The sound waves youmake when you yell have large amplitudes. The matter pushes together



a lot, so the sound is loud. Sound waves with small amplitudes arequiet. The sound waves you make when you whisper have smallamplitudes. The matter does not push together much, so the sound isquiet.

Wavelength of Sound Waves

Sound waves also have wavelength. Like the other examples of waves,the wavelength of sound waves is the distance between two crests thatare next to each other. You listen to find the wavelength of a soundwave. A high-pitched sound has a short wavelength. A lowpitchedsound has a long wavelength.

Wavelength and amplitude are independent. A police siren is highpitched and loud. A bird chirping is also high pitched but soft. Thunderis low pitched and loud. A frog croaking is also low pitched but soft.

Frequency of Sound Waves

Sound waves also have a frequency, which is how many crests pass aspecific point in a certain amount of time. Many people measure thefrequency of sound waves as how many crests enter your ear in asecond.

In all waves, frequency and wavelength are dependent on each other.Two things are dependent when they affect each other. Thewavelength of a wave affects its frequency. More waves will pass agiven point in a certain amount of time if a wave has a shortwavelength. So, a wave with a shorter wavelength will have a greaterfrequency. A wave with a longer wavelength will have a smallerfrequency. High-pitched sounds have a high frequency. Low-pitchedsounds have a low frequency.



The frequency of a sound wave is how many crests pass a specificpoint in a certain amount of time. If you had the right tools, you couldmeasure the frequency of a sound wave by counting how many wavesentered your ear in a certain amount of time.

LESSON SUMMARY

What Are Some Properties of Waves?

1. The Properties of Water Waves Amplitude, wavelength, and



frequency are properties that describe water waves. Amplitude isthe height of the water wave. Wavelength is the distance betweenthe crests of a water wave. It is also the distance between thetroughs of a water wave because these distances are the same.Frequency is the number of crests that pass a specific point in acertain amount of time.

2. The Properties of Waves on a String Waves on a string have thesame three properties that water waves do. Amplitude is the heightof the waves on strings. Wavelength is the distance between thecrests of waves on strings. Wavelength and amplitude areindependent of each other. Frequency is the number of waves thatpass a certain point in a certain amount of time.

3. The Properties of Sound Waves Sound waves have the same



properties as water waves and waves on strings. Amplitude is howloud a sound wave is. Wavelength is the pitch of the sound wave.Frequency also affects the pitch of a sound because wavelength andfrequency are dependent. This is true of water waves and waves ona string, too.

SUPER SIMPLE SCIENCE

Doing the Wave

If you have ever been to a sporting event, you may have done “TheWave.” What does The Wave have in common with waves that travelthrough water or strings?

On August 23, 2008, people cheered as they watched a world recordbeing set at Bristol Motor Speedway in Bristol, Tennessee. But it wasnot a racecar setting a record. It was the fans in the crowd. The 157,574fans were doing the stadium wave, also known as The Wave. Once thewave traveled around the entire stadium, the people there had set therecord for the largest stadium wave.

Sports fans use The Wave tocheer on their team. Aperson stands, raises herarm, and then sits backdown. Each person standsright after the person next tothem does.

The wave in Bristol was not only the world's largest stadium wave. Itwas also a very fast one. The stadium is 0.8 km (0.5 mi) around, andthe wave swept around it in just 58 seconds. So the Bristol Wavetraveled at a swift 48 kilometers per hour (30 miles per hour)!

To make a stadium wave, you need a group of people. Each personstands up, raises his or her hands, and sits back down. Each personstands up just after the person next to them does. How long has thestadium wave been used at sporting events? Who invented this crowd



pleaser?

Krazy George led the first Wave seen on television in 1981.

The Origin of the Stadium Wave

Not everyone agrees on when The Wave was first done in a stadium.But professional cheerleader “Krazy” George Henderson claims to haveinvented the stadium wave. During a 1981 baseball game, Hendersondecided to try something new. He told three sections of people to standup, one after another. He hoped to trigger a wave that would go aroundthe whole stadium.



These days, the stadiumwave is performed at alldifferent kinds of sportingevents. Here, fans performthe wave at a soccer game.

The first two tries did not work. The wave stopped part way. But soonthe fans realized what Henderson wanted. So, on the third try, the wavecircled the entire stadium. By the fourth try, the fans had mastered TheWave. “The place was going nuts,” Henderson said.

Since then, the stadium wave has spread all over the world. It becameparticularly popular after soccer fans did The Wave during the 1986World Cup in Mexico. Today, fans of many sports do The Wave, whichhas become a symbol of sport enthusiasm.

Other people say that they did The Wave before Henderson did. But thewave that Henderson led in 1981 was the one seen on television. Forthat reason, Henderson is usually given credit as its inventor.

Properties of Stadium Waves

Waves such as water waves, string waves, and sound waves all haveproperties. Some of these properties are amplitude, frequency, andwavelength.

Amplitude looks at how much matter moves from its rest position. Doesa stadium wave have amplitude? Sure it does. The amplitude of astadium wave is the number of people standing at once compared tothe rest position, where everybody is sitting. The more people whostand, the larger the amplitude of the stadium wave is.



A stadium wave has the sameproperties as other waves. Ifa wave goes all the wayaround a stadium, thewavelength is the distancearound the stadium.

Stadium waves also have frequency. Frequency is how often a wavepasses a certain point. To measure the frequency of a stadium wave,you could measure the time needed for the wave to return to itsstarting point. Suppose that a stadium starts behind home plate. Thewave circles the field and returns to home plate in 1 minute. So, thefrequency of the stadium wave is 1 wave per minute.

Stadium waves also have wavelength. Wavelength is how long a waveis. If only one wave travels around a stadium at a time, its wavelengthis the distance around the stadium. The stadium in Bristol is 0.8 km (0.5mi) around. So the wavelength of the world's largest wave was 0.8 km!

Scientists and Stadium Waves

You may think that stadium waves have nothing to do with science.But, in 2002, a team of scientists from Hungary thought that they couldlearn something from stadium waves.

The scientists used several methods to study stadium waves. First, theyanalyzed videos of stadium waves to build a model. They decided thata person could be in one of three states while doing a stadium wave. Aperson could be sitting, standing, or sitting back down. Then, the teambuilt a computer model of a stadium wave. They tested and observed itmany times, and discovered many things.

The team discovered that as few as 30 people are needed to start a



stadium wave. So, if enough of your friends are at a game, you couldwork together to start a wave. Another discovery was that a stadiumwave is more likely to happen when the game is boring. So, don't try tostart a wave when something exciting is happening.

The stadium wave is more than just a sports tradition. It is a wave thathas the properties of other waves. The next time you do The Wave,observe the details. Science is everywhere—even at the big game!

Like a water wave, a stadium wave starts in one spot and spreadsoutward. Unlike a water wave, a stadium wave spreads out on only oneside.



What Are Some Properties of Waves? · 2020-03-13 · Sound waves also have these three properties....

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