physics 30 waves
what is the difference between a longitudinal wave and a transverse wave
a longitudinal wave moves forward in a straight line, the coils are closer together. a transverse wave moves side to side with the coils further apart.
what happens after the wave hits the stationary end of the spring
the wave rebounds back to the other end. longitudinal repeats the same motion back, transverse repeats the same also but with less force
can you change the shape or speed of the wave by moving the end faster or further
when moving the end of the spring faster, the wave will be faster and more forceful, with a more defined shape. changing the distance will also cause it to be faster, because there is less distance for the wave to travel.
what is a wave
an oscillation of energy that travels through a medium
what is oscillation
regular and periodic variation of energy, predictable and consistent pattern of highs and lows.
what types of energy do waves carry
many types: the springs carry kinetic energy, and we see sound waves and electromagnetic waves
what is a medium
whatever the wave is moving through, whatever is carrying the wave. same wave may have a different speed and wavelength in a different medium
what do waves move
energy, but do not move matter. the particles of the medium bump into each other and transfer the energy, then return to original position
how can waves be observed
continuous periodic waves, or as a wave pulse- a single packet of transferred energy
what is a longitudinal wave
the particles of the medium move in parallel to the transfer of energy. can be observed as patterns of compression and rarefaction. ex) sound waves
what is a transverse wave
the particles of the medium move perpendicular to the transfer of energy. has the sinusoidal wave shape like a body of water. ex) electromagnetic waves
what is the peak of a transverse wave
highest point
what is the trough of a transverse wave
lowest point
what is the equilibrium of a transverse wave
midpoint of the wave, halfway between peaks and troughs
what is the amplitude of a transverse wave
vertical distance from equilibrium to a peak or trough
what is the wavelength of a transverse wave
length of one cycle of a wave. most easily calculated as the horizontal distance between two peaks or troughs
what is wave velocity
the speed at which the energy is transferred through the medium
what does the speed of a moving object depend on
d=vt
the distance travelled and the time required to travel it
what does the speed of a wave depend on
v=fλ
1. the wavelength
2. the frequency (inversely proportional to time)
what is the frequency of a wave
number of cycles a wave completes each second (Hz)
f=1/T
f= cycles/second
what is the period of a wave
amount of time it takes for the wave to complete one cyle, the recuprocal of the frequency.
T=1/f
T= seconds/cycle
what happens when a wave hits a boundary
they are reflected. type of boundary affects characteristics of reflection
what is a hard boundary and how is it reflected
being held in place and unable to move, when hitting a hard boundary, wave is reflected with opposite polarity
what is a soft boundary and how is it reflected
formed when the end of the medium is free to move. reflected with the same polarity
what remains the same in both hard and soft boundaries
speed and amplitude
what happens when a wave hits the boundary between mediums when travelling from one medium to another
1. part of the wave is transmitted through to the new medium
2. part of the wave is reflected back into the old medium
3. the properties of the wave change based on the densities of the mediums
explanation when wave transmits from a less dense to a denser medium
after wave hits the boundary, we see a transmitted component in the new medium and a reflected component in the old medium.
transmitted has less speed, wavelength and amplitude, reflected has same speed and wavelength, less amplitude. the wave acts as if it hit a hard boundary
explanation when wave transmits from a denser to a less dense medium
after wave hits the boundary, we see a transmitted component in the new medium and a reflected component in the old medium.
transmitted has higher speed and wavelength, same or greater amplitude
reflected has same speed and wavelength, less amplitude
wave acts like it hit a soft boundary, polarity of reflected wave stays the same
what is interference and what is how is the result found
when multiple waves act on the same particle in the medium. according to principle of superposition, result of two interfering waves can be found by adding amplitudes while noticing polarity of each. displacement of a particle is the sum of displacements caused by each wave individually
what is constructive interference
if interference results in a bigger wave.
two moving toward each other same polarity - one big wave - two moving away from each other same polarity
x+x=2x
what is destructive interference
when interference results in a smaller wave
two moving toward each other, opposite polarity - no wave - two moving away from each other, opposite polarity
-x+x=0
what is a standing wave
when waves medium has two reflecting ends, principles of superposition and reflection combine to standing wave. occurs when two waves of exact same λ, f, amplitude are travelling in opposite directions through the medium. when they meet, they create unmoving points called nodes. between the nodes are antinodes, points where the amplitude of point or trough is doubled.
how big are nodes
1/2 wavelength
why are standing waves not produced in swimming pool with people in it
despite two reflecting ends, each person produces own waves as they move. interference patterns are too complex and inconsistent for standing wave
what is refraction
if the wave hits the boundary at an angle, it changes direction of the wave. amount of refraction depends on materials and angle of incident wave
index of air and water
1.00, 1.33