Transcript Types of Waves - Dorman Freshman Campus

Waves, Electromagnetic
Waves, Light, and Sound
Waves
• is a disturbance
• moves through a medium from one
location to another location
• A medium is a substance or material
which carries the wave.
General Wave
Properties
• All waves are traveling
disturbances.
• All waves transfer energy
from place to place.
Parts of a wave
• Crest and Trough
-The section of the wave that rises above the
undisturbed position - crest
-That section which lies below the
undisturbed position - the trough
Amplitude
•
position of the medium to the top of a crest or
trough.
• Height of the wave
positive and negative
amplitudes
Different amplitudes
Wavelength
*crest to next crest, trough to next
trough,
* from the start of a wave cycle to the
next starting point
*Wave to wave
Ex: for wave length
Types of Waves
There are three types of waves:
-Mechanical waves.
-Electromagnetic waves
-Matter waves
Mechanical waves
• require a material medium to travel (air,
water, ropes).
• These waves are divided into three
different types.
– Transverse waves
– Longitudinal waves
– Surface waves
Transverse Waves
• is perpendicular to the direction of wave propagation
• Ex: light, heat, & water waves
.
Longitudinal Waves
•
is parallel to the direction of wave
propagation
Compression and Rarefaction
Compression
• Wave that has no crests or troughs
• Region where the medium become crowded or
dense
• Compress – close together.
• Sound waves & shock waves
Rarefaction
• The less dense region
Water Waves
• involve a combination of both longitudinal and
transverse motions
• particle indeed travels in a clockwise circle as
the wave passes.
Electromagnetic waves
• do not require a medium to travel (light,
radio
Matter waves
• are produced by electrons and particles.
Pulse and traveling or periodic
wave
•
a single vibration is produced is a pulse.
• moving regularly up and down, is a
traveling or periodic wave .
Measuring Waves
• The number of vibrations per second is
called frequency
• Speed of the wave=Frequency X Wavelength
• is measured in hertz (Hz).
The Wave Formula
• Velocity = Wavelength x Frequency .
.
• V = l x f
• Velocity(m/s), Wavelength (m),
Frequency (hz)
The Nature of Sound
• Sound is caused by vibrations
• Sound waves are Compression waves
• Cannot travel through a vacuum – no
particles to push around
– Travels faster through liquids and solids than
gases…why?
– Travels faster through warmer than cooler
substances…why?
Properties of Sound
• Key Sound Terms
– Frequency: How many wavelengths pass a
point each second; hertz (Hz); high
frequency=high pitch; humans 20-20,000 Hz
• Pitch: How high or low a sound seems to be
– Intensity: Amount of energy that flows through
a certain area in a specific amount of time
• Loudness: Human perception of intensity
• the symbol f is frequency
• the symbol T is used for period,
• these equations are also expressed as:
Differences in Frequencies
Wave speed
Light wave- faster than sound
Ex: flying ball reaches your eyes before the
sound wave created by the bat and ball
Depends on the medium
• Ex: sound waves travel faster in liquids than
solid
• Ex: Light waves travel slower in liquids and
solids
Calculating the wave speed
• Speed = Wavelength * Frequency
• Speed-v, Frequency-F
• And Wave length -
The Nature of a Sound Wave
*Sound
is a mechanical wave
*Sound is a Pressure Wave
*results from the longitudinal motion of the
particles of the medium
Compression and rarefaction
• -As the compression (high pressure)
• -rarefaction (low pressure)
Sound
• Measuring intensity of Sound
– Intensity is the amount of energy in the wave
– Unit of intensity is the decibel (dB)
– Above 120 dB cause pain and hearing loss
• Doppler effect
– The change in pitch or wave frequency due to a
moving wave source
– Examples
– Either the source or the observer can be moving
Doppler effect
• Doppler effect can be observed for any
type of wave
• Ex: water wave, sound wave, light wave,
etc
• the pitch of the siren sound was high;
after the car passed by, the pitch of the
siren sound was low. That was the
Doppler effect
eardrum into vibration motion.
Sound/Music
• Noise vs. Music
– Noise—random patterns and pitches
– Music—sounds deliberately used in a regular pattern
• Musical Instruments
– String vibrations of strings working with a resonator
that amplifies the sound
– Brass and woodwinds vibration of air in column
working with a resonator; holes and valves or
changing the length of the air column
– Percussion vibration of the membrane causes air
inside to vibrate
Sound
• Ultrasound
– Medicine high frequency sound waves to
detect and monitor such things as pregnancy,
heart disease, and cancer;
– can be used to break up kidney stones and
gall stones
Radio Communication
• Radio transmission
– Each station is assigned a unique frequency
(called a carrier wave)
– FM (frequency modulation); AM (amplitude
modulation); higher frequencies than AM
– Article page 405
Behavior of Waves
• Types of Interference
– Occurs when two waves combine into one
– Constructive: the wave gets bigger because
the crest and trough overlap
– Destructive: the wave gets smaller because a
crest and a trough overlaps
Properties of Sound
Intensity:
Is the amount of energy that flows
through a certain area in a specific
amount of time.
High intensity carries high energy
Loudness:
Is the human perception of the intensity.
The intensity of the sound increases, the
loudness of the sound you hear increases.
Ultrasonic wave
• Humans can’t hear sound frequencies
above 20,000 Hz, called ultrasonic waves.
• Used in medical diagnosis and treatment.
Infrasonic waves
• Is also called subsonic wave
• Have frequencies below 20 Hz
• Too low to hear
• May feel them as a rumble inside your
body
• Resonance:
• is the ability of the medium to vibrate by
absorbing energy at its own natural
frequency.
• Resonance helps amplify the sound
created in many musical instrument
• Music:
• Is made of sounds that are deliberately
used in a regular pattern.
• Musical instruments contain strings ,
membranes or columns of air- something
that vibrates at its natural frequency to
create a pitch.
• Natural frequency depends on the string’s
thickness and length and how tightly it is
stretched