 # Describe a Wave. Chapter 14 Waves & Energy Transfer.

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Describe a Wave

Chapter 14 Waves & 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

Crest Trough Amplitude 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 Behavior When waves pass from one medium to another they are both transmitted & reflected

Radio waves travel at 3.00 x 10 8 m/s. Calculate the wavelength of your favorite radio station.

Wave Behavior Waves transmitted from one medium to another stay in phase or do not invert

Wave Behavior The 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 Behavior When 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: v wave 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

Node A point in a medium that goes through no displacement when waves pass through each other

Node A point in a medium that goes through no displacement when waves pass through each other

Antinode A point in a medium that goes through maximum displacement when waves pass through each other

Standing Wave The 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 Reflection When a wave strikes a boundary at an angle other than normal, the reflected angle equal the angle of incident

Law of Reflection  reflection =  incident  

Refraction When a wave strikes a boundary at an angle other than normal, the angle of the transmitted ray is changed

Refraction The bending of waves passing from one medium to another due to speed change

Less Dense Medium More Dense Medium Normal

Diffraction The bending of waves around a barrier

Diffraction When 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 10 8 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 10 8 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.