unit 5, part 1: sound. waves swbat explain how waves are created and identify the different types of...
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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.
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
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 vibration
Any more examples?
Properties of Sound
Amplitude: how loud or soft a sound is. Measured by how
much the medium is disturbed
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.
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
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
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
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.
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