Dec. 2 – New Unit: Waves and Sound

Congratulations on finishing the Energy Unit!

I'm testing out a new app from google that will allow me to collect forms and information.  I would really appreciate it if you try it out.  If it works, we can do formative quizzes and other neat stuff in the future.  Please click on the link and try out this new tool:

• http://goo.gl/forms/Vcflxyb49K

Time for a New Unit!

Unit 4: Waves and Sound

• Unit Outline

Most important information...

• Next Test date is Dec. 16

First of all, what is this?

These people are doing a "wave", but what exactly is moving? Their arms go up and down, but what is moving from left to right?  We discussed this today in class using springs and videos:

Here are the notes and definitions from today's class.

Definitions:

Wave - A disturbance or variation that transfers energy from point to point.

Particles of the material are not being transferred, only the energy.

Examples:

 - springs

 - water

 - microwaves

 - sound

Ripples are an example of water waves.

Microwaves are an example of electromagnetic waves.

Mechanical Waves vs. Electromagnetic Waves

 - Mechanical waves have a medium that carries them. e.g. sound is carried by air (air is the medium)

 - Electromagnetic waves do not require a medium.

More Definitions:

 - Wave pulse: a single disturbance

 - Amplitude: The size of the disturbance (always positive)

 - Equilibrium: the state of the medium with no disturbance.

 - Crest: the point of maximum amplitude

 - Trough: the point of maximum negative amplitude.

 - Wavelength: the distance between two crests (or two troughs), “lambda”

 - Frequency: number of pulses per second.

    units are “per second” = Hertz

    1 / second = 1 Hz

Ex: You breath 20 per minute.  What is the frequency of your breath?

20 / min 20 / min ( 1 min / 60 seconds )   <-- write it as a fraction to see how minutes cancel             = 0.333 /s              = 0.333 Hz
You are breathing at 0.333 Hz.

Transverse vs. Longitudinal Waves

Transverse: the disturbance is perpendicular to the direction of the wave.

Longitudinal: the disturbance is parallel to the direction of the wave.

   - compression: the point of maximum density

   - rarefactions: the point of minimum density

   Eg: Sound is a longitudinal wave.

Just for fun...

Here's the difference between AM and FM radio waves: