physics terms: 4/6/06
Terms
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- resonance
- when a driving frequency matches a natural frequency of the material, interference causes large amplitude standing waves in material (shattering mirror bc of a voice)
- Huygen's principle
- "every point on a wave acts as a new wave source"
- Interference
- based on super postition prniciple (waves of similar frequency can combine new waves.)
- Constructive interference
- where amplitudes of single waves combine to create larger amplitudes
- coherent wavees
- same frequency and phase (constructive)
- anti-nodes
- max amplitude where constructive interferences occur
- nodes
- stationary points/ where total destructive force is occurring. Nodes increase with N
- diffraction
- spreading of a wave from a small opening or corner
- mechanical waves
- (sound) amplitude is a displacement of matter pressure variations
- electromagnetic waves
- (light) amplitude is an oscillating E field
- wave
- transfer of force through a medium without moving mass through medium
- tone
- wave shape and how it changes, but fundamental frequency always stays the SAME
- reflection
- bouncing of a wave off of a rigid smooth surface (theta intimate vs. theta refelcted) same value
- refraction
- a change in the direction of wave travel ("wave is bent") as wave enters new material or properties of material change i.c. troops marching, man calling a dog. refraction direction: wave bends into material where velocity is going towards lower velocity. solid surface has higher celocity, softer surface has lower velocity
- dispersion
- small dependance of velocity on wave frequency. white dividing into red and blue. seismic waves can be caused by detonating bombs
- A
- amplitude, maximum displacement
- V
- velocity, speed and direction of a wave, units : m/s, km/s
- lambda
- wavelength
- T
- time length
- Doppler Effect
- shorter wavelength, larger frequency. The amplitude(crests) of the sound waves are hitting your ear more frequently. the fdetected are larger than the fsource
- why are the strings for lower notes in stringed instruments larger and heavier than the strings for higher notes? If the mass per unit length were doubled, what happens to the frequency?
- wave pulses travel slower in a string with larger unit masses, lower velocities on a string of set length will vibrate with lower freqencies. increasing the mass by a factor of 2 does not lower frequency of 2 bc a sq root is involved
- as velocity in increases...
- wavelength increases
- why does tightening a string on a musical instrument raise the pitch of a string? What happens to the frequency if the length is reduced by a factor of 2
- tightening a string also reduces the wavelength of the standing waves. All other thing sstay the same, reducing the wavelength by two doubles the frequency
- as velocity gets lower...
- so does frequency ex. notes on large musical instrument
- large muscial instruments generally produce lower nots bc the standing waves set up on these...
- have longer wavelengths and lower frequencies ex. heavy strings