Waves & VibrationsWaves & VibrationsPhysical Science

Waves are common!Waves are common!

• Examples of waves:– Sound waves, visible light waves, radio

waves, microwaves, water waves, sine waves, cosine waves, telephone cord waves, stadium waves, earthquake waves, waves on a string, and slinky waves

Queen Elizabeth’s “wave”

WavesWaves

• Anything that moves side to side, back and forth, or front to back and transfers energy from one place to another.

Most common:

Sound waves

Ocean waves

Light waves

How Waves TravelHow Waves Travel

• When waves travel through a solid, liquid, or gas, they are called Mechanical Waves.– Common examples are SOUND waves– The matter which the wave travels through is

called a MEDIUM.

How Waves TravelHow Waves Travel

• Waves that can travel through empty space are called Electromagnetic Waves.– Electromagnetic waves include all light

waves, microwaves, xrays, and radio waves.– Electromagnetic waves do not require a

medium.

• (refer to reference chart)

Shapes of WavesShapes of Waves

• Waves can be described using two models:– Transverse Waves– Longitudinal (also called compression) Waves

• These two labels describe the way in which the wave moves.

Types of WavesTypes of Waves

• Transverse Wave– Particle motion is perpendicular to direction of

energy travel

Types of WavesTypes of Waves

• Transverse Wave– A stadium wave is an example of a transverse

wave

Parts of a Transverse Wave

Parts of a Transverse Wave

Orientation Transverse Wave

Orientation Transverse Wave

• Visible light is one type of transverse wave

Types of WavesTypes of Waves

• Longitudinal Waves– Particle motion is parallel to direction of

energy travel

Parts of a Longitudinal Wave

Parts of a Longitudinal Wave

Types of Longitudinal Waves

Types of Longitudinal Waves

• Sound is one type of longitudinal wave

Types of WavesTypes of Waves

• Surface waves are actually combinations of transverse and longitudinal waves– Water waves are a common combination

wave

Types of WavesTypes of Waves

• Earthquakes are also a result of both types of waves

Other terms to know…Other terms to know…

• Frequency– How many waves per second– Measured in Hertz (Hz)

Frequency & WavelengthFrequency & Wavelength

• The higher the frequency, the lower the wavelength. This relationship is called Non linear, Inversely Proportional.

Check your understanding!Check your understanding!

1. What transfers energy from one place to another?

2. What is matter called that a wave passes through?

3. What are the two waves a wave travels?

4. What are the two shapes of waves?

5. What is the relationship between frequency and wavelength?

Check your understanding!Check your understanding!

1. What transfers energy from one place to another?

2. What is matter called that a wave passes through?

3. What are the two waves a wave travels?

4. What are the two shapes of waves?

5. What is the relationship between frequency and wavelength?

wave

medium

Mechanical and electromagnetic

Transverse and longitudinal

Non linear, Inversely Proportional

Is light a wave or a stream of particles?Is light a wave or a stream of particles?

• The debate has been going on for centuries!

• Light exhibits both particle-like and wave-like behavior

There are unique behaviors of wavesThere are unique behaviors of waves

• Interference

• Polarization

• Diffraction

• These behaviors are dependent on BARRIERS, or anything that interrupts the travel of the wave.

What happens when two waves meet?What happens when two waves meet?

• When two waves meet in the same medium, the waves interfere.

• There are two possibilities– Constructive Interference– Destructive Interference

Types of InterferenceTypes of Interference

• Constructive Interference– Crest meets crest OR trough meets trough– Results in increased AMPLITUDE

Types of InterferenceTypes of Interference

• Destructive Interference– Crest meets trough– Results in decreased AMPLITUDE

Diffraction can be used to see colorDiffraction can be used to see color

Different light sources have different colors contained within them!

Different light sources have different colors contained within them!

Standing WavesStanding Waves

• Standing waves are a result of waves that reflect back upon themselves making a pattern of constructive and destructive interference.

PolarizationPolarization

PolarizationPolarization

• Polarization is caused when light is filtered based on the direction of movement of the wave.

Check your understanding!Check your understanding!

1. What is anything that interrupts the pattern of a wave?

2. What is it called when light is passed through a vertical or horizontal filter?

3. What is it called when a wave passes through a narrow slit?

4. What happens during destructive interference?

Check your understanding!Check your understanding!

1. What is anything that interrupts the pattern of a wave?

2. What is it called when light is passed through a vertical or horizontal filter?

3. What is it called when a wave passes through a narrow slit?

4. What happens during destructive interference?

barrier

polarization

diffusion

a crest meets a node and they cancel each other out

How do waves interact with barriers that they can not go around?

How do waves interact with barriers that they can not go around?

• They can be REFLECTED

• They can be ABSORBED

• They can be TRANSMITTED through something called REFRACTION

Reflection Absorption TransmissionReflection Absorption Transmission

The Law of ReflectionThe Law of Reflection

A

B C

D

The Law of ReflectionThe Law of Reflection

• Where is the incident wave?• Where is the reflected wave?• Where is the angle of incidence?• Where is the angle of reflection?

• A• D• B• C

Remember visible light?Remember visible light?

Why do we see the color red?Why do we see the color red?

The color redThe color red

Diffuse vs. RegularDiffuse vs. Regular

• Observe the different surfaces:

Specular ReflectionSpecular Reflection

Diffuse ReflectionDiffuse Reflection

• Rough Surface

What about black and white?What about black and white?

White reflects all colors

Black absorbs all colors (turns energy into heat)

What is Refraction?What is Refraction?

• Refraction is when a wave changes from one medium to another.

• It is caused by the need to change speed in different substances.

Refraction WavesRefraction Waves

RefractionRefraction

Total Internal ReflectionTotal Internal Reflection

Refraction Partial Reflection

Total Internal Reflection!

Check for understanding!Check for understanding!

1. What are the three things light can do when it encounters a barrier it can not go around?

2. What color is an object that absorbs all wavelengths of light?

3. When a wave of light goes from air to water, it is called __________.

4. When 100% of the light wave is reflected due to a critical angle of incidence, it is called __________________.

Check for understanding!Check for understanding!1. What are the three things light can do when it

encounters a barrier it can not go around?

2. What color is an object that absorbs all wavelengths of light?

3. When a wave of light goes from air to water and changes speed, it is called __________.

4. When 100% of the light wave is reflected due to a critical angle of incidence, it is called __________________.

Absorption, reflection, transmission

black

refraction

Total internal reflection

ImagesImages

• Images are formed by transmission of light waves that replicate a barrier (any object).

• Two kinds:– Real

• images are projected onto a screen• Images are upside down

– Virtual• Images are reversed right to left• images are right side up

ImagesImages

• Images can be formed by either mirrors or lenses.

Basic Shapes

ImagesImages

• Images can be formed by either mirrors or lenses.

ConvexConcave

Plane

ImagesImages

• Creation of images is a combination of refraction and/or reflection.

LensesLenses

Converging LensesConverging Lenses

Image Distance

Concave LensesConcave Lenses

How do you see?How do you see?

Light REFLECTS off an object

Light REFRACTS through lens of

eye

Light is ABSORBED by the

rods and cones and transmitted to

the brain

HearingHearing

• Hearing is a result of the vibrations of the inner ear bones

• Humans have 3 ear bones: the stirrup, the anvil, and the hammer bones

• Humans can detect sound at a billionth of a centimeter displacement

• Humans can suffer hearing loss at about 1 billion times that threshold

Decibel ScaleDecibel Scale

SourceIntensity

Level# Times

Greater Than TOH

Threshold of Hearing (TOH) 0 dB 100

Rustling Leaves 10 dB 101

Whisper 20 dB 102

Normal Conversation 60 dB 106

Busy Street Traffic 70 dB 107

Vacuum Cleaner 80 dB 108

Large Orchestra 98 dB 109.8

Walkman at Maximum Level 100 dB 1010

Front Rows of Rock Concert 110 dB 1011

Threshold of Pain 130 dB 1013

Military Jet Takeoff 140 dB 1014

Instant Perforation of Eardrum 160 dB 1016

Doppler EffectDoppler Effect

• The Doppler effect is when the sound source is moving– Examples include a blaring horn, sirens– Incoming sound waves are usually louder &

higher frequency– Outgoing waves (after the car has passed),

are lower frequency and softer

Doppler EffectDoppler Effect

Sonic BoomSonic Boom

• When an airplane travels fast enough to exceed the speed of sound, it produces a sonic boom– A sonic boom is the result of the “piling up” of

compression waves– This creates a high pressure area that is

followed by a bunch of rarefactions (low pressure) and the BOOM!