s)

Waves are oscillations and they transport energy.

Medium: The matter through which a wave travels

2 Subsets of Waves:

• Mechanical

waves that require a medium to travel through

(sound, water, earthquake• Electromagnetic waves that do not require amedium to travel

(light)

Most waves are caused by vibrating particles• Energy is transported, but the particle simply vibrate

in one small area

Waves are classified according to the direction inwhich the particleswave passes

in the medium move as the

2 Types:TransverseLongitudinal

Transverse WaveParticle motion is

perpendicular to thedirection of wave motion

Examples• water waves

• light waves• earthquake S-waves

Types of Waves

Wavelength =

length or size of one full oscillationAmplitude = from sitting wave to a crestCrest = highest point in the waveTrough = Lowest point in the waveResting State = The very middle, as if there were

no waves

Wave

motion

Longitudinal waveParticle ... _" moron ~

High dens

ity

LowdensityParticle motion is parallel

(a) P-wavto the directionmotion

of wave

Examples: compression rarefaction

I I~ J

• sound waves

• earthquake P-waves

I~~~I~~~I~Figure 1: Longitudittal '''ave

-.Compression

/t

•.•••.•• ....•

t·•·••·•·

••

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Compressions – Wave length

area where the mediumRarefaction –

is pushed close together

area where the mediumcompression

~,

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J

apart

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F1igure 1: lon.~itudinal \"ave

Remember that thevibrating left and

moleculesright, NOT

are simplymoving from one

end to the other

http://www.ffn.ub.es/~albert/ones/wavemotion.html

λ= wavelength (meters (m))length or size of one oscillation

velocity (m/s)how fast the wave is traveling

frequency (Hertz (Hz))

of a wave

v =

f =How many full wavelengths per second occur

Measure from any identical two successive pointsSymbol for wavelength is lambda(λ)

and is measured in meters (m)

(m)5 10 15 20 25 30 35 40

Oscillation = 1 complete wave cycle There are 4 complete oscillation depicted

here

The distance from one crest to the next crest, orfrom one trough to the next trough.It can be between any two successive points actually!

Can exist in a longitudinal wave from onecompression to the next compression.We will only concentrate on TRANSVERSE waves.• --

•

::411

cR

Frequency = number of WAVES passing a stationarypoint per second

Symbol is f Measured in Hertz (Hz)

λ= v/f

λ = wavelength (meters (m))length or size of one oscillation

velocity (m/s)how fast the wave is traveling

frequency (Hertz (Hz))

of a wave

v =

f =How many full wavelengths per second occur

~~.

= v/f

The string of a piano that produces the note middle

C vibrates with a frequency of 262Hz. If the sound waves produced by this string have a wavelength in air of 1.3m, what is the speed of the sound waves?

λ= v/f1.3m = v /

262Hz340.6m/s =

v

Remember, a wave is just transporting energy! The 2 ways to increase the energy a wave carries.

• 1) Increase the amplitude of a

• 2) Increase the frequency of a

wave

wave(done by decreasing wavelength)

I

http://phet.colorado.edu/sims/wave-on-

a-string/wave-on-a-string_en.html .I.I I I 'II .1.

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http://www.youtube.com/watch?v=z0EaoilzgGE

Change in frequency of a wave due to relativemotion between source and observer.• A sound wave frequency change is noticed as a

change in pitch.

Basically, as an object making noise moves closerto you, the pitch of the noise will increase• Because the sound waves are compressed upon each other

As an object making noise moves away from you,the pitch of the noise will decrease• Because the sound waves are further away from each other

Sound normally occurs like this from a stationaryobject

B A

With a moving object, the sound being producedis not moving to each side evenly.

.

http://faraday.physics.utoronto.ca/PVB/Harrison/Flash/ClassMechanics/Doppler/DopplerEffect.html

http://galileoandeinstein.physics.virginia.edu/more_stuff/flashlets/doppler.htm

Electromagnetic Spectrum

Wave - Review

Waves are oscillations that transport energy.

2 Types of waves: Mechanical – waves that require a medium to travel

through (sound, water, earthquakes)

Electromagnetic – waves that do not require a medium to

travel (light)

Nature of Electromagnetic Waves

Electromagnetic waves: are waves that travel without a medium.

(They can travel through empty space) They travel as vibrations in electrical and magnetic

fields.

Speed of electromagnetic waves = 300,000,000 m/s

OR 300,000km/s

Takes light 8 minutes to move from the sun to earth {93 million miles} at this speed.

Vocabulary Recap/Help Page

Wavelength – The distance from crest to

crest of a wave. How long the wave is in

meters.

Frequency – The number of waves that

pass a point in one second. Determines

the energy a wave has. Measured in

Hertz.

The Electromagnetic SpectrumElectromagnetic Spectrum—Consists of

waves at all possible energies, frequencies, and wavelengths. They are placed in order of increasing frequency

So what do we notice about the wave as we move further right on our diagram?

Radio Waves

Radio waves have the longest wavelengths and lowest

frequency in the electromagnetic spectrum. Wavelengths range from .1m to 100km

Used by Radios, TVs, RADAR systems, Cell Phones

Each radio station broadcasts in a different frequency Cellular phones use radio waves that are much smaller than TV

and FM radio waves.

Used by long range communications,

wireless networks, bluetooth, some

A microwave oven works by passing

and absorbed by the water/fat/sugar

in

against each other.together???

Microwaves

microwaves, cell phones, pagers,

radar detectors.

microwave radiation, through the food,

the food. The energy causes the food particles to vibrate

What’s the by product of things rubbing

THERMAL ENERGY!

cold objects

Infrared Light (below red)

IR light from the sun is what keeps

you warm Uses: remote controls, the

bottom of your mouse, night vision,

target acquisition and tracking by the military and short-ranged

wireless communication.

Thermography: test method that

records thermal patterns and temperatures across the surface

of an object. Warm objects give off more energy

than

eye.

yellow 570–590 nm

not present, but are a

Visible Light The ONLY portion of the violet 380–450 nm

EMS which can be blue 450–495 nm

detected by the human green 495–570 nm

Some colors like brown, orange 590–620

nm

pink, and magenta are red 620–750 nm

blend of different wavelengths. ―White light‖ can be broken down into each of the individual colors by using

a prism.

layer, more harmful types of UV light is blocked.

and burn.

Ultraviolet

(beyond violet) UV Light carries more energy than visible

light Because of absorption in the atmosphere’s ozone

This type of wave is what causes your skin to tan

Used in tanning beds and black lights Too much can cause skin cancer. Some birds (birds of prey) and bees can see in the UV light spectrum Used to kill bacteria. (Sterilization of equipment) Causes your skin to produce vitamin D

(good for teeth and bones in moderation)

Use sun block to protect against (UV rays) UV rays are also what cause ―sun bleaching‖when certain materials are left outside

shorter than ultraviolet.

imaging.

the less dense

tissues but

cause cancer

X-Rays

Waves longer than gamma,

Widely used in medical

Carry a great deal of energy

Has enough energy to

pass not bone. Teeth and Bones absorb x-rays

Too much exposure can

MOST ENERGY of entire EMSradiation emitted by a nuclear explosioncause serious damage when absorbed by living

Gamma Rays

Smallest Wavelength (Highest Frequency) =

Gamma rays are the most dangerous form of

Due to their high energy content, they are able to

cells. Naturally occur in:

Radioisotopes on Earth (Radium, carbon-14, uranium-235, etc)

Fission and fusion reactionsproduce

it Sun spots (most all of

radiation absorbed by atmosphere)

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What type of electromagnetic waves have the most energy?

What type has the longest wavelength?

What type has the highest frequency?

What visible light has the longest wavelength?

What visible light has the lowest frequency?

by Bill AP1~lld

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Waves can interact with other waves, otherobjects, or change medium (travel throughdifferent substances) When a wave meets a new surface or boundery,

wave reflects

the

When athrough

When a

wave passes the edge of an object or passesan opening, the wave diffracts

wave passes from one medium to another atan angle, it will refract

Reflection is the bouncing back ofa wave when it hits a surface or boundary that is hard enough that it can’t travel through. Examples: water waves bouncing off

of a boat, images in a mirror (and glass or very still water), echos.

Light obeys the “Law of Reflection” The angle of incidence will equal the

angle of reflection

Flat Surfaces (like mirrors) Every single incident ray will

hit at the same angle, and bounce off at the same angle

Rough Surfaces (like wateror frosted glass) Every single incident ray will

hit at a different angle, and scatter when they reflect

Diffraction: When waves pass theedge of an object, or reach an

opening, they will bend or spread:

spread out as if they were created there ( for small openings)

bend around the object (when waves pass an edge)

Refraction: The bending of waves when they

pass from one medium to the next Occurs when waves reach a new medium (that ittravel through) at an angle.▪ Medium = the material the wave is traveling through

can

Each time a wave reaches a new medium, they aredeflected (change direction) as they change speed

The pencil looks broken because of refraction: The light traveling to/from the part of the pencil out of the water

does not everchange speeds. The light that travels to/from the part of the pencil in the waterhas to change speeds (and changes angles) as it enters the water. This causes light from each end to reach your eye at different angles.

Different substances have different angles ofrefraction

ie: Waves bend/change directions at different angles when

they enter that specific substance This is because waves travel at different speeds in

differentsubstances

The slower light travels through an object, the more light

will “bend” and change direction when it enters it

A laser and a glass cubeOnly wavelength, so it can’tseparate into different wavelengths- That single wavelength slows down in

the glass cube to the left

White Light and a PRISMWhite light is made of ROYGBIV, many

different wavelengths. It canseparate into different wavelengths

- Each wavelength slows down at a different rate, separating in the prism to the right

Light slows down when it enters a prism and “bendsdown” when it strikes at this angle. Each wavelength of light slows down and bends differently. Violet end slows down more than the red end, so it bends

more. When light exits the prism, it speeds back up and

bends down again.

Water will do the same thing… it will refract light.

When light enters water, it will slow down (or bend) This causes objects underwater to appear as if they are

somewhere else. The light is tricking your eye.

Water will do the same thing… it will refract light.

Sometimes waves will interact with other waves…

Interference: When several waves are in the same

location, they combine to produce a single, new

wave that is different than the original wave

Once the waves pass through each other, they willtheir original shape and continue on their path.

return to

2

types

Constructive (add to each other)

Destructive (cancel each other out)

When the CREST of one wave overlaps the CREST of

another wave the waves reinforce each other

These wave are also called “in phase” When this happens, the amplitude INCREASES

http://www.acs.psu.edu/drussell/demos/superposition/sup

erposition.html

When the CREST of one wave overlaps the TROUGH of

another wave, the resulting wave has a SMALLERamplitude than the larger of the two original waves

When this happens, the waves can even cancel out These wave are also called “out of phase”

http://www.kettering.edu/physics/drussell/Demos/superposition/superposition.html

A lens is an optical device with symmetry

transmits AND refracts light We have 2 types of lenses:

that

Convex (converging) and

concave

(diverging)

We can either use:

A Simple Lens: one lens

▪ Examples: reading glasses,

magnifying glass, your retina

A Compound Lens: uses more than one lens

▪ Examples: telescope, microscope, cameras, etc

Lenses caneither be: Convex

(converging)

OR

Concave (diverging)

An eye that can see at20/20 vision will allowlight to focus directlyat the back of theretina.If you don’t see 20/20,your focal point is notdirectly on the retina,and you get a blurryimage

To correct nearsighted eyes (myopia), you use concave lenses They move the focal

point backward To correct farsighted

eyes (hyperopia), glasses will be made with convex lenses They move the focal

point forward.