Waves and Wave Properties Presentation for lesson 2: Waves and Wave Properties, in the Waves: The Three Color Mystery unit The slides are animated so you can click (space bar, mouse, etc.) to show the next item when the class is ready. Waves and Wave Properties

If a tree falls in the forest and there’s no one there to hear it, does it make sound? The falling tree still makes a vibration in the air causing a wave so on one hand there is a sound wave, but if no one is there to receive the wave and transfer it into a tone, then there can be no true sound.

Longitudinal/Compression vs Transverse Wave Longitudinal/Compression wave needs a medium – it is a mechanical wave. Transverse wave needs a medium – it is mechanical wave also, but a electromagnetic waves is also type of a transverse wave that does not need a medium. (such a light) http://www.acs.psu.edu/drussell/demos/waves/wavemotion.html http://www.fearofphysics.com/Sound/dist.html

Loudness A measure of how well a sound can be heard. This is called Amplitude High Amplitude Low Amplitude High Amplitude Low Amplitude Loudness is directly related to amplitude. The larger the amplitude, the louder the sound. Amplitude- the maximum distance that the particles of a wave's medium vibrate from their rest position

20 3. Amplitude: How far the medium moves from rest position (where it is when not moving). . http://www.educationscotland.gov.uk/resources/s/sound/amplitude.asp?strReferringChannel=resources&strReferringPageID=tcm:4-248294-64

Pitch A measure of how high or low a sound seems to be. Pitch is directly related to frequency. The higher the frequency the higher the pitch. Frequency- the # of waves produced in a given amount of time. http://www.ndt-ed.org/EducationResources/HighSchool/Sound/frequencypitch.htm

Wave Properties Wave properties can change depending on what is making the waves or causing the wave Wavelength: The distance between one point on a wave and the exact same place on the next wave. http://www.solpass.org/science4-5/sound/sound-standards.html

The higher the frequency, the more energy in the wave. 2. Frequency: How many waves go past a point in one second; unit of measurement is hertz (Hz). The higher the frequency, the more energy in the wave. 10 waves going past in 1 second = 10 Hz 1,000 waves go past in 1 second = 1,000 Hz 1 million waves going past = 1 million Hz 1 http://www.classzone.com/books/ml_science_share/vis_sim/wslm05_pg18_graph/wslm05_pg18_graph.html

A mathematical way to calculate speed: 21 4. Wave speed: Depends on the medium in which the wave is traveling. It varies in solids, liquids and gases. A mathematical way to calculate speed: wave speed = wavelength x frequency (in meters) (in Hz) OR v = f x ג Problem: If a wave has a wavelength of 2 m and a frequency of 500 Hz, what is its speed? Answer: speed = 2 m x 500 Hz = 1000 m/s Answer: speed = 2 m x 500 Hz = 1000 m/s

Parts of transverse waves: Crest: the highest point of the wave Trough: the lowest point of the wave Amplitude: Height of the wave Wavelength: distance between any two crest or compressions.

Compressional/Longitudinal Wave 13 Compressional/Longitudinal Wave A wave in which the vibration of the medium is parallel to the direction the wave travels

"Seeing" Sounds An oscilloscope can graph representations of sound waves. The graphs look like transverse waves instead of longitudinal waves.

Which sound is louder?

Which sound has a lower pitch?

Mechanical waves Need: Need a source of energy! That energy causes a vibration to travel through the medium

Transverse Wave (s) Transverse waves: a wave that moves at right angles to the direction of the wave. Can be mechanical or electromagnetic. 11

Parts of longitudinal waves: 15 Parts of longitudinal waves: Compression: where the particles are close together Rarefaction: where the particles are spread apart

Transverse and Longitudinal Wave Which is which?

Types of Mechanical Waves, ctd. Transverse Longitudinal Surface: A wave that travels along a surface separating two media