CHARACTERISTICS OF WAVES Chapter 15, Section 2, pp 514-523.
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Transcript of CHARACTERISTICS OF WAVES Chapter 15, Section 2, pp 514-523.
CHARACTERISTICS OF WAVES
Chapter 15, Section 2, pp 514-523
A. __________
• Represents the amount of __________ carried by the wave
AMPLITUDE
•The maximum movement of a wave from ________.
• Measured from rest to ________ (top of the wave) or rest to __________ (bottom).
REST
CRESTTROUGH
ENERGY
Ex: A sound wave with more energy and greater amplitude is __________LOUDER!
Earth Harp
AM
PL
ITU
DE
• The intensity of an earthquake is determined by the _____________ of the original disturbance and waves.
AMPLITUDE
• Earthquake energy measured by a
_________________.SEISMOMETER
• The distance between two equivalent parts of a wave. Ex: from ________ to ________
CREST
B. ______________WAVELENGTH
CREST
• Symbol = ___
(Greek letter _______)
Lambda
• unit = ______meter
• shorter wavelengths carry _______ energy than longer wavelengths.
MORE
C. _______PERIOD
• the time (seconds) required for one full _____________ of a wave to pass a certain point.
• Ex: Time between crests in a wave pool
WAVELENGTH
D. ________________FREQUENCY• The number of complete waves per unit of time (waves/second)
• Unit = _________.
• Distinguishes one color of ______ from another, or whether or not a _______ is audible.
Hertz (Hz)
SOUND LIGHT
• 1 Hz = 1 vibration / sec
Frequency = 1
T (period)
Frequency vs. PeriodFrequency Period
• How often something happens
• Time it takes something to happen (start to finish)
• Rate quantity • Time quantity
• Cycles/second • Seconds/cycle
Example: If the woodpecker drums upon a tree 2 times in one second, then the frequency is 2 Hz. Each drum must endure for one-half a second, so the period is 0.5 s.
Different colors…• In the same medium, light travels at the _____ speed (300,000,000 m/s or 186,000 mph). What makes the colors different? ___________
SAME
frequencies…
the frequencies…
• Ex: Humans hear from 20-20,000 Hz
• Mosquito ring tones
SAME
Different sounds…• In the same medium, sound travels at the
______ speed. What makes differently pitched (high/low) sounds? _______________
• For two waves moving at the SAME
speed, as INCREASES, frequency ____________DECREASES
• In addition, as the period of a wave decreases, the frequency _____________ (INVERSE relationship)
INCREASES
Wave Speed• The speed of a wave depends on the ________.MEDIUM
• In a given medium, the speed of a wave is ____________.CONSTANT
1500 m/s 340 m/s3,800 m/s
WHY DOES SPEED DIFFER?
The speed of a wave is equal to wavelength divided by period, or to frequency multiplied by wavelength.
Remember…
the speed of a moving object is found by dividing the ________ the object travels by the ____ it takes the object to travel that distance
or…
speed = distance / time
(v = d / t)
distancetime
So… wave speed = wavelength ÷ period
• Because wave speed is the inverse of frequency, dividing by the period is equivalent to multiplying by the frequency.
• Therefore the speed of a wave can also be calculated:
wave speed = frequency × wavelength
v = λ T
v = f x λ
V
λ
T
f
V
λ
Practice ProblemThe string of a piano that produces the note middle C vibrates with a frequency of ____ Hz. If the sound waves produced by this string have a wavelength in air of ____ m, what is the speed of the sound waves?
Given: Unknown:
frequency, f = 262 Hz wave speed, v = ? m/s
wavelength, λ = 1.30 m
262
1.30
Equation =
Solution:
v = 262 Hz x 1.30 m
v = 341 m/s
v = f x λ
Variables: v= ? f= 262 Hz λ= 1.30m
The Doppler Effect• An observed change in the ____________ of a wave when the source of the wave or the observer is _________MOVING
FREQUENCY
Train Horn Doppler
Fire Engine Siren Doppler
BLUESHIFT
REDSHIFT
Doppler Big Bang
More wave speed practice problems
1. The average wavelength in a series of ocean waves is _____ m. A wave crest arrives at the shore on average every ____ s, so the frequency is ______ Hz. What is the average speed of the wave?
15.0
10.0 0.100
2. Green light has a wavelength of __________ m. The speed of light is _________ m/s. Calculate the frequency of green light waves with this wavelength.
0.523,000
3. The speed of sound in air is about _____ m/s. What is the wavelength of a sound wave with a frequency of _____ Hz (on a piano, the A below middle C)?
340220
4. Calculate the frequency of microwaves that have a wavelength of _______ m and a speed of _________ m/s.
0.0085 3,000