Unit 5, Part 1: SOUND

WAVES SWBAT explain how waves are created and identify the different types of waves

What do you already know about sound and waves? (10 minutes total) Create a CIRCLE thinking map Write “Sound & Waves” in the center Think about your point of views. Where have you learned about sound and waves before? What words, images, or examples come to mind? SHARE your thinking map with a partner. 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 Examples Any more examples? When we talk, our vocal chords move. When we play the guitar, the string moves When you hit a drum, the drumhead moves 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 Loudness

Amplitude Determines Loudness Higher Amplitude = Louder Lower 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 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 is the number of waves produced in a given time Frequency of Waves Frequency 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

THE CREST IS THE HIGHEST PART OF THE WAVE!

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.

THE DISTANCE BETWEEN WAVE HEIGHT AND WAVE TROUGH

THE TIME IT TAKES FOR ONE WAVE TO PASS 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…

frequency and period have an inverse relationship f = 1 or T = 1 T f Frequency (f) = hertz (H) Period (T) = seconds (s)

Wave Speed We can determine wave speed using wavelength and frequency v = fλ V = wave speed f = frequency λ = wavelength

But, don’t worry about those calculations!

…YET!

Exit Ticket Draw a wave and label the CREST, TROUGH, and RESTING point In one sentence, explain how one would calculate a wave’s height In one sentence, explain how one would calculate wave length Sounds need to travel through a __________. What is wave amplitude? Write a 3-5 sentence summary about today’s lesson.