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 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- must have matter to move through called a MEDIUMMechanical Waves- must have matter to move through called a MEDIUM 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)
What is a Wave? What is the medium for waves at the beach?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 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 the medium for waves in a football stadium?
What is a Wave? What is the medium for waves that cause an earthquake?What is the medium for waves that cause an earthquake?
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
2 nd Type of Mechanical Wave Longitudinal Waves a.k.a. Compressional WavesLongitudinal 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?