WAVES

WAVESTypes of Waves and Their Properties

1Waves KWLWhat do you know about waves?What have you learned about waves?3 things minimum!

Where do/have you encountered waves in your everyday life?

Be specific//give details!

Answer this section throughout the unit, any time you learn something new or cool!

Be sure to give details!What do you wonder/ want to know about?3 things minimum!

Be specific//give details!

Questions of the WeekWhat is a wave?

What kinds of waves are there?

Waves Are Everywhere!!!Waves are disturbances that transfer energy through matter or space.Energy is the ability to do work.

There are 2 main types of waves:1) Waves that require a medium to travel throughWaves that need a medium are called mechanical waves.A medium is the material (matter) in which a mechanical wave travels.A medium can be a solid, liquid, gas, or a combination.All waves that travel through a medium have a source.

2) Waves that are able to travel without a mediumeg. electromagnetic (light) waves can travel through a vacuum (empty space where there is nomatter), but can also travel through a mediumWe will learn more about EM waves when we talk about light later in the Unit.

Khan Academy Introduction to Waves

4Mechanical WavesMechanical waves are created when a source of energy causes a medium to vibrate or oscillate.Vibrations are repeated up-and-down or back-and-forth movement of molecules or objects

Sound and water waves travel through a medium. The medium requires matterA medium can be a solid, liquid, gas, or a combination of these.

There are 3 types of mechanical waves, based on the direction the wave moves:longitudinal, transverse, and surface

Vibrations Video #1

Vibrations Video #25Transverse WavesA transverse wave is when matter in the medium moves at right angles (perpendicular, 90, or up and down) to the direction the wave travels.eg. a rope, electromagnetic radiation (light), seismic waves (earthquakes)

The crest is the highest part of the wave.

The trough is the lowest point of the wave.

Rest is where the wave would be if it wasnt moving (in the middle of the crest and the trough).

Transverse wave videoBrightstorm - Transverse Waves

6Longitudinal WavesA longitudinal wave (compression wave) is when matter in a medium moves in the same direction (parallel or back and forth) that the wave travels. eg. slinky; sound

A compression is when the medium is pushed close together (or is more dense).

A rarefaction is when the medium is pulled farther apart (or is less dense).

Longitudinal wave videoTransverse vs. Longitudinal waveBrightstorm Longitudinal Waves

7Types of Mechanical Waves

Surface WavesA surface wave is a combination of the two types of waves (longitudinal and transverse). The particles move in a circular motion.

It occurs between two mediums; for example air and water.

Water moves back and forth slightly but can not compress

BrainPop - Waves

9Check Your UnderstandingAnswer the Question of the Week.

Read What are Waves?

Answer questions 1 to 19 in your notebook.

Compare and contrast the following: a) Longitudinal and transverse waves b) Mechanical waves and electromagnetic waves.

Complete the following sentences:Something important that I have learned about waves is; I would like to know more about; Some new terms I need to remember are

Optional: Complete the Facts Only! graphic organizer in your notebook.

Facts Only! (written in complete sentences; in your own words)

Main Idea5 Supporting Facts(a sentence 1. written in2. your own 3. words)4. 5.Question of the WeekIf waves are similar to one another, how can we tell them apart?

Properties of WavesThere are many different types of waves (eg. sound, light, etc.), but all waves have the same basic shapeWaves share certain properties

What distinguishes one wave from another are:The amplitude (height) of the waveThe wavelength (distance) of the waveThe frequency (number of waves in a certain time)The speed (how fast) at which a wave travels

Khan Academy Amplitude, Frequency, and Wavelength of Waves

Which Wave Has More Energy?When you go surfing, do you try to catch:

A little wave

Or a BIG wave?

AmplitudeThe amplitude of a wave is the height of the crest or the depth of the trough (they are the same). In a transverse wave, amplitude is the distance from rest to crest (or rest to trough) but not crest to trough!In a longitudinal wave, amplitude is how compressed a wave is.

The larger the amplitude, the greater the energy a wave has. The smaller the amplitude, the less energy a wave has.

Amplitude videoWave Characteristics video

Which wave has the highest amplitude?

WavelengthThe wavelength () is the distance between two corresponding parts of the wave eg. in a transverse wave, it is measured from crest to crest, or from trough to trougheg. in a longitudinal wave, it is measured from compression to compression or from rarefaction to rarefaction

Wavelength is measured in meters (m)

Wavelength video

FrequencyThe frequency (f) of a wave is the number of times the wave passes a certain point in a given timeIt is measured in vibrations/sec or Hertz (Hz)

1 Hz = 1 vibration/sec or 1 wave/sec

eg. If a string vibrates three times in 10 seconds, what is the frequency?3 vibrations/10 seconds= 0.3 vibrations/sec= 0.3 Hz

Brightstorm - Frequency

Which wave has the highest frequency? Why?

Frequency Questions1. Use the two waves on the right to answer the following questions:a) What are the frequencies of these waves if they pass by in 10 seconds?b) What are their frequencies if they pass by in 1 second?

2. What happens to the frequency of a wave if we change the wavelength?As the wavelength decreases, the frequency increases. and vice versa: as the wavelength increases, the frequency decreases.

Waves Song

17Important Facts About WavesLight travels about 300 000 000 m/s (300 000 km/s)!Sound travels about 340 m/s (in air).The speed of a wave depends on the properties of the medium the wave is traveling in. eg. Sound travels faster in solids or liquids than in a gas

As long as waves travel through the same medium, their speed is unaffected by a change in wavelength or frequency because as one increases, the other decreases

The higher the amplitude of a wave, the larger its energy

The longer the wavelength, the lower the frequency and the lower the pitch (pitch is highness or lowness of sounds)

18Check Your UnderstandingAnswer the Question of the Week.

Read Properties of Waves

Answer Questions 1 to 19

Optional:Complete the Textbook Survey Graphic Organizer for 5 facts you came across in the reading.

Check out this wave simulation (also on Moodle) to help you understand what amplitude is and also the relationship between frequency and wavelength.

Textbook Survey Graphic Organizer:For each of your 5 facts:

Fact: (Write the fact in your own words)Comment/Reaction/Opinion:(Write a comment, reaction, or opinion to the stated fact)Question: (Write a question to yourself that will help you to remember the fact)

Question of the DayHow can we calculate the speed, frequency, or wavelength of a wave?

Brightstorm - Wave Speed

Wave CalculationsWhen talking about Energy, we learned that velocity is how fast something is moving.velocity = distance time(or v = d/t)units: m/s = m s

When we talk about waves: the distance is wavelength of the wave (in meters); andthe time is the inverse of the waves frequency (in 1 s or 1/s) [another name for this is the period (T)]

So the equation to find the speed of a wave becomes:speed = wavelength x frequency or in other words: v = x f

When we rearrange the formulas to solve for x f: v x feg. A wave has a wavelength of 1 m. If it has a frequency of 10 Hz, how quickly is it traveling?knowns: f = 10 Hz; = 1 munknown: vv = x fv = 1 m x 10 Hzv = 10 m/s

Wave CalculationsA sound wave is traveling at 340 m/s. If the frequency is 68 Hz, what is the wavelength?

If a microwave has a wavelength of 5 mm and travels 300,000 km/s, what is its frequency?Wave CalculationsA sound wave is traveling at 340 m/s. If the frequency is 68 Hz, what is the wavelength?knowns: f = 68 Hz; v = 340 m/sunknown: v = x f = v/f = 340 m/s 68 Hz = 5 m

If a microwave has a wavelength of 5 mm and travels 300,000 km/s, what is its frequency?knowns: = 5 mm, v = 300,000 km/sunknown: fMust convert to SI units (eg. meters) = 0.005 m, v = 300,000,000 m/s v = x ff = v/ f = 300,000,000 m/s 0.005 mf = 60,000,000,000 /s (or Hz)Check Your UnderstandingComplete the practice questions on the next slides

Summarize in 1 paragraph (4 to 5 sentences in your own words) what you have learned about the properties of waves.

Complete Wave Calculations Assignment (Moodle)

Practice Wave Calculations1. A 100 waves pass by every 20 seconds. What is the waves frequency?

2. Calculate the velocity of a wave if its wavelength is 30 cm and its frequency is 150 Hz.

3. Find the wavelength of a wave if it travels at 10 m/s and has a frequency of 8000 Hz.

4. What is the frequency of a light wave that has a wavelength of 30 mm?

5. A wave travels 13 km in 6.5 seconds. What is its velocity?

Practice Wave Calculations1. A 100 waves pass by every 20 seconds. What is the waves frequency?0.2 Hz2. Calculate the velocity of a wave if its wavelength is 30 cm and its frequency is 150 Hz.45 m/s3. Find the wavelength of a wave if it travels at 10 m/s and has a frequency of 8000 Hz.0.00125 m4. What is the frequency of a light wave that has a wavelength of 30 mm?1 x 1011 Hz (or 100 000 000 000 Hz)5. A wave travels 13 km in 6.5 seconds. What is its velocity?2000 m/s

Practice Wave CalculationsMac and Tosh are resting on top of the water near the end of the pool when Mac creates a surface wave. The wave travels the length of the pool and back in 25 seconds. The pool is 25 meters long. Determine the speed of the wave.

While hiking through a canyon, Noah Formula lets out a scream. An echo (reflection of the scream off a nearby canyon wall) is heard 0.82 seconds after the scream. The speed of the sound wave in air is 342 m/s. Calculate the distance from Noah to the nearby canyon wall.Question of the DayWhat happens to a wave when it encounters an obstacle or another wave?Wave Behaviour and Other PhenomenaWhen a wave travels through a medium, it will often encounter the end of the medium or some other obstacle.

This obstacle affects the way that the wave behaves.

ReflectionReflection occurs when a wave hits a reflective surface and the wave changes direction and bounces back.

Law of reflection - the angle of incidence = the angle of reflection.eg. Ball hits wall, look in mirror, echo

30RefractionRefraction is the change in direction of a wave due to a change in its speed. This happens when a wave goes from one medium to another

When a wave moves from one medium to another at an angle, it changes speed and bends.

NOT the same thing as rarefaction in a longitudinal wave

31DiffractionDiffraction is the bending of waves around the edge of a barrier.eg. sound bends around corners

Because of change of speed, waves can bend in different patternsThe amount of bending increases with increasing wavelength and decreases with decreasing wavelength

BrainPop Refraction vs. Diffraction

32InterferenceInterference occurs when two or more waves meet and interact with each other

Constructive interference - when two waves combine to make a wave with a larger amplitude.Constructive Interference Video

Destructive interference -when two waves meet and make a wave with a smaller amplitude or cancel each other out.Destructive Interference Video

33Standing WaveA standing wave is a wave that appears to stand in one place (constant position)This happens when two waves traveling in opposite direction interfere with one another

A node is a point where the amplitude of the wave is zero

An antinode is the maximum energy in the wave (the crests and troughs)

Standing Wave VideoStanding Wave Video #2

34ResonanceMost objects have a natural frequency of vibration.

Resonance is when vibrations traveling through an object match the objects natural vibrations.

If vibrations of the same frequency are added, the amplitude increaseseg. a swing (if you time the pushes properly, the swing moves with a large amplitude)eg. breaking a wine glass

Many of the sounds we hear, such as when hard objects are struck (metal, glass, wood, etc), are caused by brief resonant vibrations in that object.

35Check Your UnderstandingAnswer todays Question of the Day.

Read Waves Interactions.

Complete the Picture Response Chart graphic organizer in your notebooks for the following:ReflectionRefractionDiffractionInterference (constructive and destructive)Standing WaveResonance

Draw a picture for each interaction

Answer questions 1-26Picture Response Chart:Describe what you seeIn your OWN wordsExplain what is happening and whyDraw a pictureExample: Reflection