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