chapter 16-17 Flashcards
what are longitudinal waves and examples?
- motion of medium is parallel to propagation
- sound waves, compressed spring, seismic P waves
what are transverse waves and examples?
- motion of medium is perpendicular to propagation of wave
- waves on a string, ripples on water, seismic S waves
does the shape of the wave matter for its speed?
no, it is independent of the shape
can w be negative?
no
what to do when asked a velocity at specific t or specific x or both?
partial derivative of y with relation to t
what to do when asked the formula when the wave moves only to right or only to left?
use y = f(x-vt) + g(x+vt)
how to find the wave speed from a formula?
w/k
what is constructive interference?
y1 and y2 have the same sign (so same side up/down) = they reinfore
what is distructive interference?
y1 and y2 have opposite signs (one is up side up and other is upside down) = smaller wave (like subtraction)
what happens after any interference of 2 waves?
they pass through one another unaffected
what is the reflection of a wave on a string with a fixed end?
reflected pulse is inverted up/down and left/right
what is the reflection of a wave on a string with a vertically free end?
the reflected wave is inverted left/right but NOT up/down
what is the reflection when there is the junction of 2 strings?
- partial reflection and partial transmission
- smaller A than original
what does it mean when waves are out of phase?
same A, w, k, but different phase constant
what is the maximum possible new A when waves are added?
2A (when the cos (phase2 - phase1) / 2 = 1)
what is completely destructive interference?
when the phase difference between the two = odd multiple of pi (y1 and y2 cancel)
what are standing waves?
- supposition of two harmonic waves with same A,w,k but opposite directions of travel (different sign before w)
- y tot (x,t) = 2Asin(kx)cos(wt)
- only move up/down
what can you change to change a note of an instrument (to change f)?
- tension (higher T = higher f)
- mass/length (mu) (higher mu = lower f)
- length (smaller length = higher f)
what are waves of pressure?
medium compressed and expands
how does the density and rigidity affect the v?
- more rigid = v higher
- more dense = v lower
what are sound waves?
- longitudinal waves
- diplace air
how can the intensity be defined?
- power/perpendicular are
- variation of pressure compared to 1 atm
what are dB?
logarithmic scale to measure a wide range of audible intensities
what happens to B as I is multiplied?
- I multiplied by 10, B increases by 10
- B increases by 30, I multiplied by 10x10x10 = 1000
