LASERS Does anyone have lasers at home they

LASERS Does anyone have lasers at home they can share with me for a few days? We can use them for doing a lab on wave behaviors next week

Waves • How energy travels from one place to another • (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 space

Mechanical Waves • Mechanical Waves- must have matter to move through called a MEDIUM • Sound waves • Earthquake waves • What is a medium (any kind of matter disturbed by the energy of a wave)

What is a Wave? • What is the medium for waves at the beach?

What is a Wave? • What is the medium for waves coming out of your television?

What is a Wave? • What is the medium for waves in a football stadium?

What is a Wave? • What is the medium for waves that cause an earthquake?

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

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

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

Parts of a Transverse Wave • Crest: highest point of the wave • Trough: 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

nd 2 Type of Mechanical Wave • Longitudinal Waves a. k. a. Compressional Waves – Sound Waves – Some Earthquake Waves

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

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

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

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

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: 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. Vw = f λ (units: meters/second, or equivalent) Look at that formula – if Vw stays the same. What can you say about f and λ?