Waves Jun8

Happy Monday!

June

th 8

2015

Today’s Agenda:

• Notes & PowerPoint • Waves Video Ac?vity • Wave Exit Ticket

Today’s Objec.ves:

• Classify a Mechanical wave as Transverse, Longitudinal, or Surface • ID the parts of a wave: wavelength, amplitude, crest, trough, compression, rarefac?on, & rest posi?on

Waves • Have you ever been in a wave pool at an amusement park? How do we know that energy is being transferred?

Mechanical waves • A mechanical wave is a _disturbance __________ in maMer that carries _energy _____ from one place to another • Energy is the ability to do _work ____ • Mechanical waves need a material to travel through, which is called a _medium _______ • A medium can be a solid, _liquid ___, or gas

In a wave pool, what is the medium? water

Mechanical waves • A mechanical wave is created when a source of energy causes a vibra?on to travel through a medium • Think about shaking a rope, when you shake the rope, you add energy o The wave that results carries energy along the rope

Mechanical waves • Mechanical waves are classified by the way they move through a medium

3 transverse longitudinal

surface

Wave Diagram Crest Rest position

Trough

Transverse wave • Before the wave, every point is @ res.ng posi?on • The highest point of the wave above the RP is the _crest ____ • The lowest point below the RP is the _trough _____ • The crest and the trough are not fixed points • A transverse wave is a wave that causes the medium to vibrate at right angles to the direc?on in which the wave travels

Transverse wave • Imagine shaking a rope aMached to a chair o By shaking the rope, you create waves that move up and down o However, the energy is moving from le? to right o These two mo?ons are perpendicular to one another

Transverse wave

Transverse wave • Examples of transverse waves: o Shaking a rope up & down that is ?ed to

something o Shaking crumbs off of a blanket or sand off of a beach towel o Stadium wave at football & basketball games

transverse waves • In transverse waves, the vibra?on of the medium is _perpendicular __________ to the direc?on that the wave travels

Longitudinal : w a Dr

waves

compression

rarefaction • However, in a longitudinal wave, the vibra?on of the medium is parallel to the direc?on the wave travels

Longitudinal

waves

• To start a LW, add energy via pushing & pulling o carries energy from leS to right, coils move closer together or farther apart

Longitudinal

waves

• Think about a slinky or a spring o When you push it together and pull it apart, a wave is sent through the slinky o Each coil in the slinky vibrates back-­‐and-­‐ forth, the wave also travels back-­‐and-­‐forth o Therefore, the mo.on of the vibra.on is parallel to the direc.on the wave moves

Longitudinal

waves

• Slinky Drop Experiment: https:// www.youtube.com/watch?v=wGIZKETKKdw

Longitudinal

waves

• Label each sec?on as a compression or rarefac.on compression compression A C E compression

rarefaction B

• Remember,

rarefaction D

o A compression is an area where the par?cles in a medium are spaced _close _____ together o A rarefac.on is an area where the par?cles in a medium are _spread ______ _out ___

Longitudinal • Examples? o Sound waves o P waves (earthquake)

waves

Surface waves • The first waves you probably think of is ocean waves, which are called surface waves • A surface wave is a wave that travels along a surface separa.ng two media • Ocean waves travel between water & air • A bobber in the ocean moves up & down (perpendicular) and back & forth (parallel) producing a circular mo?on

Surface waves • Most waves do not transfer maMer from one place to another • However, as a wave enters shallow water, it topples over on itself • Why do you think this happens?

• Fric.on with the show slows down the boMom of the wave • The top of the wave con?nues forward at its original speed

Surface waves

Properties of

mechanical waves • How do we describe waves?

• If you like to surf, fish, or just swim in the ocean – you should know a liMle something about describing waves...

3 ft. at 8s SE 2 ft. at 14s NE

Properties of MWs • Wavelength is the distance between a point on one wave & the same point on the next cycle of the wave

Wavelength

Wavelength • The distance between a point on one wave and the same point on then next cycle of the wave

Which wave has longer wavelengths?

A B hMps://www.youtube.com/watch? v=aH5r4ZTOXS4

Amplitude • Amplitude of a wave is the maximum displacement of the medium from its rest posi?on

Amplitude • Amplitude of a wave is the maximum displacement of the medium from its rest posi?on

• The more energy ______ a wave has, the greater its amplitude

Waves Video Activity

• For this ac?vity, students will work in groups of 4-­‐5 to create a 3-­‐5 minute video explaining the 3 types of mechanical waves discussed today • In the video, students should illustrate and define: mechanical wave, transverse wave, trough, crest, rest posi.on, longitudinal wave, compression, rarefac.on, surface wave, medium, wave length, & amptliude

Exit Ticket pg. 100 1. Draw a transverse wave. Label the crest, trough, amplitude, and wavelength.

2. Draw a longitudinal/compressional wave.

Label an area of compression and rarefac?on.

3. Give an example of a surface wave.

4. In what type of wave does the medium travel perpendicular to the mo?on of energy?

5. In what type of wave des the medium travel parallel to the mo?on of energy?