M ECHANICAL W AVES Ch 17.1. TrueFalseStatementTrueFalse There are 2 types of mechanical waves-...

MECHANICAL WAVESCh 17.1

True False Statement True False

There are 2 types of mechanical waves- transverse and longitudinal

Transverse waves have compressions and rarefactions

Longitudinal waves have crests and troughs

Surface waves separate 2 mediums

Mediums are the materials that waves travel- solids, liquids or gases

MECHANICAL WAVES Carries energy from one place to another due

to a disturbance in matter

Must have a medium Solid Liquid Gas through which the wave travels

TRANSVERSE WAVES Causes the medium

to vibrate at right angles to the direction in which the wave travels

Parts- Crest- highest point Trough- lowest

point

LONGITUDINAL WAVES Vibration of the

medium is parallel to the direction the wave travels

Parts- Compression-

particles are close together

Rarefaction- particles are spread apart

SURFACE WAVES Travels along a

surface separating 2 mediums

PROPERTIES OF MECHANICAL WAVESCh 17.2

True False Statement True False

By increasing frequency the wavelength decreases

The less energy a wave has, the more amplitude it has

Speed of a wave = wavelength x amplitude

Frequency is the # of complete cycles in a given time

The period is the time required for one wave cycle

PERIOD Time required for 1

cycle – a complete motion that returns a wave to its starting place

Periodic Motion Regular time

intervals

FREQUENCY The # of complete

cycles in a given time

Measured in hertz Hz, cycles per

second

WAVELENGTH Distance between a

point on the wave and the same point on the next cycle of wave

Transverse wave Adjacent troughs or

crests Longitudinal wave

Adjacent compressions or rarefactions

WAVE SPEED

SI Units V= f = Hz λ= m

Can change if the wave hits a new medium

If waves travel at constant speed, then wave length is inversely proportional to frequency

PRACTICE One end of a rope is

vibrated to produce a wave with a wavelength of 0.25m. The frequency of the wave is 3hHz. What is the speed?

Given:

Equation:

Solve:

AMPLITUDE Maximum

displacement of the medium from its rest position

The more energy= greater amplitude

Transverse Distance from rest

position to a crest or trough

Longitudinal Maximum

displacement of a point from its rest position

BEHAVIOR OF WAVESCh 17.3

True False Statement True False

Reflection happens due to a wave bouncing off a surface it cannot pass

through

Refraction is the bending of a wave as it moves around an obstacle or

passes through an opening

Diffraction is due to a wave hitting a new medium

Interference is when waves combine to either increase or decrease

Standing waves appear to stand still, because the waves overlap

REFLECTION A wave bounces off

a surface that it cannot pass through

It does not change the speed or frequency of the wave but the wave can be flipped or turned upside down.

REFRACTION The bending of a

wave as it enters a new medium at an angle

Happens due to one side of the wave moving slower than the other side

DIFFRACTION The bending of a

wave as it moves around an obstacle or passes through a narrow opening

INTERFERENCE

2 or more waves combine to produce a wave with larger displacement

2 or more waves combine to produce a wave with smaller displacement

Constructive Interference

Destructive Interference

STANDING WAVES Appears to stay in one place

As if not moving through a medium

Parts- Node- point with no displacement from the rest

position Antinode- point where a crest or trough occurs

midway between 2 nodes

Forms only if half a wavelength or multiple of half a wavelength fits exactly into the length of a vibrating cord

SOUND AND HEARINGCh 17.4

True False Statement True False

The lower the decibels, or frequency the quieter a sound appears

The higher the intensity the higher the pitch of sound

Sonars and ultrasound are due to frequencies lower than most people can hear

The Doppler effect is a change in sound due to a change in motion

The ear has 3 main parts, that work together to help you interpret sound

PROPERTIES OF SOUND WAVES Longitudinal waves

Compressions and rarefactions that travel through a medium

Speed Intensity Loudness Frequency Pitch

PROPERTIES OF SOUND WAVES

In dry air @ 20 °C Speed of sound=

342m/s Speed varies in

mediums Solids fastest Liquids Gas slowest

Speed

PROPERTIES OF SOUND WAVES

Intensity-rate which waves energy flows through a given area

Depends on waves amplitude and distance from the sound source

Measured in Decibels, dB

Loudness-physical response to intensity

High frequency=louder

Intensity & Loudness

PROPERTIES OF SOUND WAVES

Frequency depends on How fast the source

of the sound is vibrating

Pitch is the frequency of a sound as you perceive it

High frequency=high pitch

Frequency & Pitch

ULTRASOUND Normal sound

20Hz – 20,000Hz

Infrasound Frequencies lower

than you can hear

Ultrasound Frequencies higher

than you can hear Used for sonar and

imaging

ULTRASOUND

Technique for determining distance to an object under water

Sound Navigation and Ranging

Important in medical field

Maps heart, and babies without interfering with pulse

Sonar Ultrasound Imaging

DOPPLER EFFECT Change in sound frequency caused by

motion of Sound source Listener Or both

Closer to sound Higher frequency

Farther to sound Lower frequency

HEARING & THE EAR Outer Ear

Middle Ear

Inner Ear

REPRODUCED SOUND Sound is recorded

by converting sound waves into electronic signals that can be processed and stored.

Sound is then reproduced by converting electronic signals back into sound waves

MUSIC Instruments vary pitch by changing the

frequency of standing waves

Resonance amplifies sound The response of a standing wave to another

wave of the same frequency