1

Waves

Chapter 14

2

Types of Waves

A wave is a disturbance that carries energy through matter or space.

The medium is the matter through which a wave travels.

Waves that require medium are called mechanical waves.

3

Transverse waves

Transverse waves are waves which the motion of the particles is perpendicular to the motion of the wave.

The top of the wave is called the crest.

The bottom of the wave is called the trough.

The distance between the crest on one wave to the crest on the next is called the wavelength.

4

Longitudinal wave

Longitudinal waves are waves where the particles in the medium vibrate parallel to the direction of the wave motion.

Compressions are the parts of the wave where the medium is compressed.

Rarefactions are parts of the wave where the medium is spread apart.

The distance between compressions is the wavelength.

5

Surface waves

Surface waves occur at the boundary between two mediums.

The particles move both perpendicularly and parallel.

6

Wave Properties

Transverse waves have the shape of a sine curve.

Highest point of a transverse wave is a crest.

Lowest point of a transverse wave is a trough.

Amplitude is the greatest distance that particles are displaced from their normal resting position.

7

Wave Properties(continued)

Wavelength is the distance from one crest to the crest of the next wave.

Period is the time required for one full wavelength of a wave to pass a certain point.

Frequency of a wave is the number of full wavelengths that pass a point in a given time interval.

8

In which type of a wave does the particles travel perpendicular to the direction of the wave?

long

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surfa

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none

of the

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1. longitudinal

2. transverse

3. surface

4. none of the above

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21 22 23 24 25 26 27 28 29 30

9

What is the top part of a wave called?

am

plitu

de

com

press

ion

cre

st

trough

0% 0%0%0%

1. amplitude

2. compression

3. crest

4. trough

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24 25 26 27 28 29 30

10

What do we call is the distance between two crest on a transverse wave?

am

plitu

de

freq

uency

per

iod

wav

elen

gth

0% 0%0%0%

1. amplitude

2. frequency

3. period

4.4. wavelengthwavelength

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21 22 23 24 25 26 27 28 29 30

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Frequency-Period Equation

Frequency=1/period F=1/T Frequency is

measured in a unit called a hertz.

12

Wave Speed

wave speed=frequency x wavelength

V=f x λ

13

Doppler Effect

The Doppler Effect is the changed in the observed frequency of a wave resulting from the motion of the source or observer.

As the source is approaching the observer, the wavelength decreases and the pitch increases.

As the source is going away from the observer, the wavelength increases and the pitch decreases.

14

Reflection

Reflection is the bouncing back of a wave when it meets a surface or boundary.

15

Diffraction

Diffraction is when a wave bends around an object or opening.

16

Refraction

Refraction is the bending of a wave as it passes from one medium to another medium.

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A transverse wave…..

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Vib

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Vib

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Vib

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.

24

5

001

A. Vibrates particles perpendicular to the direction of wave

B. Vibrates particles parallel to the direction of the wave

C. Vibrates both parallel and perpendicular to the direction of the wave

D. Vibrates particles in one direction

E. I don’t get it.

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21

22 23 24 25 26 27 28 29 30

18

In the diagram, identify the wave property “A”

A. B. C. D.

1 0

29

0

A. Frequency

B. Amplitude

C. Wavelength

D. I don’t know

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21 22 23 24 25 26 27 28 29 30

19

Wave Interference

Wave interference is when several waves are in the same location and the waves combine to produce a single, new wave that is different from the original waves.

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Constructive Interference

The result of two individual waves coming together to produce a wave of greater amplitude is called constructive interference.

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Destructive Interference

The result of two individual waves coming together to produce a wave of lesser amplitude than the larger of the original waves is called destructive interference.

22

Interference

As two wave sources combine, the waves pattern changes.

23

Beats

Interference of sound waves produces beats.

The beat frequency refers to the rate at which the volume is heard to be oscillating from high to low volume.

24

Standing Waves

Standing wave is when the interference of the original wave with the reflected wave causes the medium to vibrate in a stationary pattern.

25

Standing Wave

Nodes are the areas of a standing wave where there are no vibrations.

Antinodes are areas of a standing wave where there is maximum vibration.

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Longitudinal Wave

27

Transverse

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Water Wave

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Rayleigh Surface Wave

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Review Questions

Name the three types of waves. transverse, longitudinal & surface Which type of wave has the particles

moving perpendicular to the motion of the wave?

transverse Which type of wave has the particles

moving parallel to the motion of the wave? longitudinal

31

Review Questions

Which three things can a wave do when it meets a barrier?

reflect, diffract or refract When the crest from one wave meets the

crest of another wave, what happens? constructive interference What do you call the top of a transverse

wave? crest

32

Review Questions

On a longitudinal wave, what do you call the part of the wave that is spread out?

rarefaction What is it called when the sound

approaching you gets louder and fades as it is going away from you?

Doppler Effect

33

Review Questions

What happens when the crest of one wave meets the trough of another wave?

destructive interference What type of interaction occurs when

a wave strikes a barrier and bounces back?

reflection

34

Review Questions

What is the relationship between wave speed, frequency & wavelength?

Wave speed=frequency x wavelength What do we call the interference of

waves of slightly different frequencies traveling in the same direction?

beat

35

Review Questions

What is the bottom part of a transverse wave called?

trough What is the part of the longitudinal wave where

the wave is pressed closely together? compressions What is the interaction of a wave called where

the wave changes speed as it passes from one medium to another and bends?

refraction

36

Review Questions

What is the distance between two crests on a transverse wave called?

wavelength What is the distance between a crest and

the resting position called? amplitude What do we call the number of waves that

pass a given point in a given amount of time?

frequency

37

Review Questions

What do we call the time it takes for one wave to move past a given point?

period What happens to the frequency of a wave

as the wavelength gets longer? lowers In which metric units do we measure

frequency? hertz

38

Review Questions

What is the material called that waves move through?

medium What type of wave needs a medium to

move? mechanical What do we call a disturbance that transfers

energy? wave

39

Review Questions

What type of wave is light? transverse What type of wave is sound? longitudinal What type of wave is produced when

a wave is interfered with by its reflected wave?

Standing wave

40

Review Questions

What is the part of a standing wave called where there are no vibrations?

nodes How does the medium affect the wave

speed? the closer the particles, the faster the wave

speed Where do surface waves occur? boundary between two mediums

41

Internet Cites

http://id.mind.net/~zona/mstm/physics/waves/interference/waveInterference2/WaveInterference2.html

http://id.mind.net/~zona/mstm/physics/waves/interference/waveInterference1/WaveInterference1.html

http://id.mind.net/~zona/mstm/physics/waves/partsOfAWave/waveParts.htm

http://micro.magnet.fsu.edu/primer/java/wavebasics/index.html

http://www.bbc.co.uk/schools/gcsebitesize/physics/waves/an_introduction_to_wavesrev4.shtml