Unit 5, Part 1:SOUND
WAVESSWBAT explain how waves are created and identify the different types of waves
What do you already know about sound and waves? (10 minutes total)
1. Create a CIRCLE thinking map2. Write “Sound & Waves” in the center3. Think about your point of views. Where have
you learned about sound and waves before?4. What words, images, or examples come to
mind?5. SHARE your thinking map with a partner.6. DISCUSS as a class.
Sound Waves Video (5 minutes)
Key ideas in this PowerPoint will be in RED
Thinking about sound• Sound waves must go through a medium• The medium is made up particles– Mediums can be solid, liquid, or gas
• Waves cause particles to vibrate and create sound
• A wave occurs when there is a disturbance in a medium
Vibrations
Sound is a form of energy that is produced by vibration (back-and-forth movement)
Vibration ExamplesWhen we talk, our vocal chords move.
When we play the guitar, the string moves
When you hit a drum, the drumhead moves
When we talk, our vocal chords move.
Each of these movement is a back-and-forth movement called a vibrationAny more examples?
Properties of Sound
Amplitude: how loud or soft a sound is. Measured by how
much the medium is disturbed
Amplitude Determines
Loudness
Amplitude Determines LoudnessHigher Amplitude = LouderLower Amplitude = Softer
Example: you can beat a drum with different levels of intensity. The harder you beat the drum, the more vibrations, and thus a
greater amplitude.
Loudness & Softness: The
numbers represent “decibels,” or “db.” The human ear can hear from 0db’s to
about 110db’s comfortably.
120db’s or more could result in ear
damage.
Frequency of WavesFrequency is the number of waves
produced in a given time
Types of waves
• If a wave moves perpendicular to the motion of the particle, this is called a transverse wave
Types of waves• Longitudinal waves occur when a string is
compressed and stretched.
• The stretched and compressed regions travel along the spring
• Sound waves are longitudinal because particles move parallel to wave motion
Longitudinal Waves (The Slinky Wave)• When the slinky is pressed together, we call
this compression• When the slinky is stretched, we call this
rarefaction
Parts of a wave
• Crest• Trough• Resting Point• Wavelength (λ) • Amplitude
CREST
THE CREST IS THE HIGHEST PART OF THE WAVE!
TROUGH
THE TROUGH IS THE LOWEST PART OF THE WAVE
RESTING POINT
Point “C” represents the dashed line.The dashed line is this wave’s resting point.
WAVE HEIGHT
THE DISTANCE BETWEEN WAVE HEIGHT AND WAVE
TROUGH
WAVE PERIOD
THE TIME IT TAKES FOR ONE WAVE TO PASS
Example 1
Example 2: You can see this same thing in the ocean
Example 3
Measuring Waves
• Frequency: the number of waves that pass a given point over a unit of time
• Period: time required for one complete wavelength to pass a given point
The distance between points A and point B is the “wave length”
And remember, math and science are ALWAYS related…
f = 1 or T = 1 T
fFrequency (f) = hertz (H)Period (T) = seconds (s)
frequency and period have an inverse relationship
Wave Speed
• We can determine wave speed using wavelength and frequency
v = fλ
V = wave speedf = frequency
λ = wavelength
But, don’t worry about those calculations!
…YET!
Exit Ticket
1. Draw a wave and label the CREST, TROUGH, and RESTING point
2. In one sentence, explain how one would calculate a wave’s height
3. In one sentence, explain how one would calculate wave length
4. Sounds need to travel through a __________.5. What is wave amplitude?6. Write a 3-5 sentence summary about today’s lesson.