Describe a Wave. Chapter 14 Waves & Energy Transfer

Describe a Wave

Chapter 14Waves &

Energy Transfer

Wave•A rhythmic

disturbance that carries energy through matter

Wave Pulse•A single bump or

disturbance that travels through a

medium

Continuous Wave•The rhythmic disturbance that travels through a

medium

Types of Waves

Transverse Wave•A wave that vibrates perpendicular to the

wave motion

Transverse Wave•A good

representation would be a sine wave

Longitudinal Wave

•A wave that vibrates parallel to the wave motion

Longitudinal Wave

•A good representation

would be a slinky

Surface Wave•A wave that travels

on the border of two mediums

Surface Wave•Have both transverse & longitudinal

characteristics

Surface Wave•Good examples are

swells or surface water waves

Mechanical Waves

Waves that require a medium

Electromagnetic Waves

Waves that do not require a medium

Ray•A vector

representing the wave & its direction

Measuring Waves

Wave Speed•How fast a wave is

moving through a medium

Wave Speed

v = d/t

Wave Speed•Measured in

m/s

Wave Speed•All waves move at a constant speed in

a given medium

-1

-0.5

0

0.5

1

0 2 4 6 8 10

Crest

Trough

Amplitude

Wavelength ()

Wavelength ()•The distance between corresponding points

in a wave

Wavelength ()•Measured in m or

some form of m

Displacement•The perpendicular

distance a wave vibrates from zero

Amplitude•The maximum

displacement a wave vibrates from zero

Frequency (f)()•The number of

waves per unit time

Frequency•Measured in hertz

(Hz) •(cycles/s or waves/s)

Period (T)•The time measured in (s) for one wave to pass or the time for

one cycle

Frequency Period Formula

T = 1/f

Wave Velocity Formula

v = f

You are 525 m from a clock tower. You hear a

clock’s chime at 436 Hz in 1.50 s. Calculate: v, T, & of the sound

wave

You shout towards a wall 0.685 km away producing a 75 cm wave. You hear the

echo in 4.00 s. Calculate: v, T, & f

Surface Waves•At wave boundaries

exhibiting both transverse &

longitudinal properties

Wave Speed•All waves move at a constant speed in

a given medium

Waves passing from one medium

to another

Incident Wave•The waves that

strikes a boundary of a given medium

Reflected Wave•The waves that bounces off the

boundary & returns

Transmitted Wave

•The waves that passes from one

medium to another

Wave BehaviorWhen waves pass from one medium to another

they are both transmitted & reflected

Radio waves travel at 3.00 x 108 m/s. Calculate the

wavelength of your favorite radio station.

Wave BehaviorWaves transmitted from

one medium to another stay in phase or do not

invert

Wave BehaviorThe amplitude change in

both transmitted waves & reflected waves is

dependent on % transmitted

Wave Behavior

When colliding with a more dense medium, reflected waves invert

Wave Behavior

When colliding with a less dense medium, reflected waves stay

erect or in phase

Wave Behavior

When waves pass from one medium to another

of , the frequency remains constant

Wave BehaviorWhen waves pass from one medium to another of different density, the

speed changes

Wave Behavior

The speed of longitudinal waves is

proportional to the density of the medium

Wave Behavior

The speed of transverse waves is inversely proportioned to the

density of the medium

Wave Behavior

v = f, thus is inversely

proportioned to f

A tsunami is formed 1800 km away

producing a 60 ft tidal wave that strikes shore 3.0 hr later. Calculate:

vwave in m/s

Interference

The effect of two or more waves passing through a medium

simultaneously

Principle of Superposition

At the point where 2 or more waves meet, the

total displacement is the sum of all the individual

displacements

Constructive Interference

When the interference of waves is crest to

crest

Constructive Interference

Will result in waves of larger amplitude

Destructive Interference

When the interference of waves is crest to

trough

Destructive Interference

Will result in waves of smaller amplitude

NodeA point in a medium that

goes through no displacement when waves pass through

each other

NodeA point in a medium that

goes through no displacement when waves pass through

each other

AntinodeA point in a medium that goes through maximum

displacement when waves pass through

each other

Standing WaveThe result of identical

waves moving in opposite directions

Standing Wave

A guitar string is a good example

Waves in Two Dimensions

Reflected Wave

When a wave bounces off a wave

boundary

Law of ReflectionWhen a wave strikes a

boundary at an angle other than normal, the reflected angle equal the angle of incident

Law of Reflection

reflection = incident

RefractionWhen a wave strikes a

boundary at an angle other than normal, the

angle of the transmitted ray is changed

RefractionThe bending of waves

passing from one medium to another due

to speed change

Less DenseMedium

More Dense

MediumNormal

Diffraction

The bending of waves around a barrier

DiffractionWhen a wave passes

through a small opening, the wave will exit in a semi-circular

pattern

Three waves (1.0 m, 0.60 m, & 0.50 m) pass simultaneously through

a medium. Calculate maximum & minimum

displacement:

Red light with a wavelength of 600.0 nm travels through space at

3.00 x 108 m/s. Calculate its:

frequency & period

A 60.0 Hz note from a base guitar travels

through a hot room at 360 m/s. Calculate its:wavelength & period

A series of 6.0 ft waves move towards an island.

Determine the side of the island where the

waves will be the largest. Front of back

Three waves (2.0 m,1.5 m, & 1.2 m) pass

simultaneously through a medium. Calculate

maximum & minimum displacement:

Blue light with a wavelength of 450 nm travels through space at

3.00 x 108 m/s. Calculate its:

frequency & period

An 85 Hz note from a bass guitar travels

through a room at 340 m/s. Calculate its:

wavelength & period

Island Phenomenon

Answer the questions on page 268 & 269, and

work problems a on page 269.