PICK UP 1. Papers & calculator
TURN INU6 – 4 (Wave calculations)
Progress Reports
DO NOW1. Partner up and quiz on
vocab! The timer is already
going! HW: study/review for Quiz Friday
Next Test: 2/13!
U6
Why it matters in LIFE:
Part of being a
functional human
being is being able to
understand what’s
happening in the world
around you!
Why it matters in THIS CLASS: Our Goal = 80%
Mastering today’s lesson (focused
participation, asking questions, etc)
is the first brick that will help us
reach our goal for this unit, and
eventually for the year
By the end of today, IWBAT…Describe mechanical waves and
understand sound waves in terms of
intensity, pitch, interference, and the
Doppler effect.
TEKS:
(B) investigate and analyze
characteristics of waves, including
velocity, frequency, amplitude, and
wavelength, and calculate using the
relationship between wavespeed,
frequency, and wavelength;
Topic:
Mechanical Waves
By the end of today,
IWBAT…Describe mechanical waves
and understand sound waves
in terms of intensity, pitch,
resonance, interference, and
the Doppler effect.
MECHANICAL WAVES• Mechanical waves transfer energy through a matter
medium (solid liquid, or gas).
• They cannot travel through empty space (a vacuum).
• They can be either transverse (ex: seismic) or
longitudinal (ex: sound).
SOUND WAVES
Sound waves are mechanical longitudinal waves
caused by vibrations that push the particles
around.
Stations!• 5 stations (1 set in the classroom, 1 set in the hallway)• 8 minutes per station.• Groups of 2 or 3• Time to take notes, discuss, &
answer the quick check questions.
INTENSITY
Amplitude
INTENSITY/LOUDNESSUnits decibels (dB)
- how much energy a sound wave has.
Threshold of hearing (0 dB) Threshold of pain (120 dB)
PITCH
PITCH
Determined by f, Units (Hz)
http://www.noiseaddicts.com/2009/03/can-
you-hear-this-hearing-test/
http://www.noiseaddicts.com/2009/03/can-you-hear-this-hearing-test/
INTERFERENCE
Interference - two or
more waves overlapping
to form a new wave.
INTERFERENCE
CONSTRUCTIVE INTERFERENCE
DESTRUCTIVE INTERFERENCE
SPEED OF SOUND
SONIC BOOMS
The speed of sound in air is 343 m/s.
Mach 1 = speed of sound
If you are supersonic, you are going faster that the speed of sound which creates a sonic boom!
DOPPLER EFFECT
The apparent change in the frequency/pitch of a sound caused by the motion of either the listener or the source of the sound.
When moving towards you, it sounds higher pitched; when moving away, it sounds lower pitched.
EX: police and ambulance sirens
DOPPLER EFFECT
To calculate the speed of a wave, multiply
the wavelength by the frequency.
v = λf
v = wave speed or velocity (m/s)
λ = wavelength (m)
f = frequency (Hz or 1/s)
EXAMPLEA sound wave in air has a frequency of 21,000 Hz. Calculate its wavelength.
Procedure for IP time:
1) Silent work time
2) Try and solve without notes first!
Hierarchy of who to ask
1) Your brain
2) Your notes
3) Your partner (quiet whisper)
4) Ms. Cowley
INDEPENDENT PRACTICE!
EXIT TICKET (4 MIN)1. What must a mechanical wave have to travel
through?
2. A sound wave in air has a wavelength of 5m.
Calculate its frequency.
3. Can humans hear this sound? Why or why not?
EXIT TICKET (4 MIN)1. What must a mechanical wave have to travel
through?
A medium (solid, liquid, gas)
2. A sound wave has a wavelength of 5m.
Calculate its frequency.
f = 68.6 Hz (or 1/s)
3. Can humans hear this sound? Why or why not?
Yes, because it falls within the human hearing
range of 20 – 20,000 Hz!
10 WORD SUMMARY!
