1

Recognize that all waves transfer energy.

Relate frequency & wavelength to the energy of different types of electromagnetic waves & mechanical waves.

Compare and contrast the characteristics of electromagnetic and mechanical (sound)waves.

Explain the

phenomena of

reflection,

refraction,

interference, &

diffraction.

Explain the Doppler

Effect in terms of

everyday

interactions.

Relate the speed of sound to different mediums.

2

WavesWavesWaves are disturbances Waves are disturbances

that carry that carry energy energy through matter or space.through matter or space. Clip

The material does not The material does not actually travel with the actually travel with the wave….. only the energy is wave….. only the energy is carried.carried.

Waves can be visible or Waves can be visible or invisible evidence of energy invisible evidence of energy transfer.transfer.

3

Types of WavesTypes of WavesTwo types of waves:

•Mechanical•Non-Mechanical

Mechanical: waves need a medium in order to travel.

Examples: Sound, water

Non-mechanical: waves do not need a medium to travel.

Examples: light, gamma waves, microwaves, x-rays

4

Waves that require a medium to travel.

Light waves are NOT Mechanical Waves.

Sound and water.

Mechanical WavesMechanical Waves

A medium is the material a A medium is the material a wave travels throughwave travels through

5

Ways that waves travel

•Transverse waves–Water, light

•Compressional waves–sound

6

Transverse WavesTransverse WavesTransverse waves are UP &

DOWN movements.

EX: water waves, radio waves (all EM waves)

The displacement of individual particles is perpendicular (at right angles) to the direction of the wave.

7

Describing a Transverse Wave

Crest

Trough

8

amplitude

The higher the amplitude, the more energy the wave is carryingIn a compressional wave- it’s how tightly the compressions are.

9

Frequency & WavelengthWavelengthWavelength

•Distance between to identical points on adjacent waves.•Meters•As the wavelength decreases the frequency increases

FrequencyFrequency•Number of waves per second•Hertz

10

λ

Movement of a Transverse Wave911

CLIP

Example - Water

Remember: Energy is transferred ----NOT THE MATTER!--

12

Compressional WavesCompressional waves are a series of PUSHES & PULLS in which the motion of the medium is in the same direction as the wave

Ex. Sound Waves

13

Characteristics of a Characteristics of a Compressional WaveCompressional Wave

14

Parts of a Compressional wave• Compressions &

Rarefactions

Rarefaction is a place where the Rarefaction is a place where the atmospheric pressure is lowest.atmospheric pressure is lowest.

15

Speed of a waveν = f λ

•ν is the velocity (m/s)• f is the frequency (hertz)•λ is the wavelength (m)

The speed of a wave changes as it moves through different media

The speed of a mechanical waves is constant for any given medium..

16

Let’s do some practice

problems.

ν = f λ

Wave Wave interactions interactions with matterwith matter

Wave interactions with matter

Reflection occurs when a wave hits another wave or object that it cannot pass through and bounces back.

17

Law of Reflection

18RefractionRefraction occurs when a wave passes from one

medium to another at an angle and bends (changes direction) due to a change

in speed.

Refraction

•Diffraction is a wave phenomenon that is dependent on wavelength

•Light waves bend as they pass by the edge of a narrow aperture or slit 

Diffraction occurs when a wave passes through an

opening and spreads out

19

Diffraction

•When a wave encounters an obstacle. •Apparent bending of waves around small obstacles and the spreading out of waves past small openings.

20

Constructive InterferenceConstructive Interference occurs when two or more waves hit the same point and combine to produce a larger single wave.

Destructive InterferenceDestructive Interference occurs when two or more waves hit the same point and combine to produce a smaller single wave.

Constructive InterferenceConstructive Interference

Constructive InterferenceConstructive Interference

Destructive InterferenceDestructive Interference

Clip

Recognize that all waves transfer energy.

Relate frequency & wavelength to the energy of different types of electromagnetic waves & mechanical waves.

Compare and contrast the characteristics of electromagnetic and mechanical (sound)waves.

Explain the

phenomena of

reflection,

refraction,

interference, &

diffraction.

Explain the Doppler

Effect in terms of

everyday

interactions.

Relate the speed of sound to different mediums.

2

GOALS REVISITED.