Waves How energy travels from one place to anotherHow energy travels from one place to another (you need energy to start it, and it doesn’t stop until all the energy is transferred)(you need energy to start it, and it doesn’t stop until all the energy is transferred)

What is a Wave? A disturbance that carries energy through matter or spaceA disturbance that carries energy through matter or space

Mechanical Waves Mechanical Waves- need a medium to move throughMechanical Waves- need a medium to move through Sound waves Sound waves Earthquake waves Earthquake waves What is a medium (any kind of matter disturbed by the energy of a wave) What is a medium (any kind of matter disturbed by the energy of a wave)

Two Basic Types of Mechanical Waves Transverse and Longitudinal 1. Transverse Waves1. Transverse Waves The disturbance runs perpendicular to the wave’s direction The disturbance runs perpendicular to the wave’s direction Looks more like a wave at the beach Looks more like a wave at the beach

Transverse Waves Move in an up and down motion perpendicular to the direction of the waveMove in an up and down motion perpendicular to the direction of the wave

Transverse Wave Anatomy Resting Point Trough Crest/Peak Wavelength λ Amplitude

Parts of a Transverse Wave Crest: highest point of the waveCrest: highest point of the wave Trough: lowest point of the waveTrough: lowest point of the wave

Parts of a Transverse Wave cont’d Wavelength: ( ) Distance between a point on one wave to the identical point on the next wave (One whole Wave) Amplitude: (a) Distance from the crest or trough of a wave to the resting point

Two Basic Types of Mechanical Waves 2 nd Longitudinal Waves a.k.a. Compressional Waves2 nd Longitudinal Waves a.k.a. Compressional Waves –Sound Waves –Some Earthquake Waves

Longitudinal Wave Longitudinal Wave Matter vibrates in the direction of the waveMatter vibrates in the direction of the wave Energy moves parallel to the matterEnergy moves parallel to the matter Examples: Sound waves, springs, coilsExamples: Sound waves, springs, coils

How does a Longitudinal wave work? Compressions expand to an area that is less denseCompressions expand to an area that is less dense Rarefaction: The less dense area in a compressional waveRarefaction: The less dense area in a compressional wave

How Does a Longitudinal Wave Work? (Cont’d) Wavelength ( ): One compression and one rarefractionWavelength ( ): One compression and one rarefraction

When Waves Hit Things Reflection: The wave bounces off the new medium and can change direction

Refraction Refraction: The wave enters a new medium and changes speed This is responsible for “weirdness” when you look at things through water – magnification, warping, etc…

Diffraction Diffraction: The wave bends around corners or edges of a barrier

Frequency of a wave Frequency: the number of waves that pass a point in a given amount of time. Measured in Hertz (Hz)

Speed of Waves Wave speed is equal to the frequency of the wave times the wavelength. V w = f  λ (units: meters/second, or equivalent) Look at that formula – if V w stays the same. What can you say about f and λ?

Also – just for reference… Sound travels at 1087 feet per second (about 1/5 mile per second) Light travels at 186,000 miles per second Take home message: light travels MUCH faster than sound. You see something before you hear it. Example: lightening and thunder

Energy Poster Questions 1.What do almost all of the energy sources have in common when it comes to converting to electricicty? (what method) 2.Pick 2 sources you like and choose 2 interesting things from each of those 2 sources. 3.Are the two you picked renewable energy? If not, what are they?