Waves Flashcards
what’s a progressive wave
it’s a wave that carries energy from one place to another without transferring any material
what’s transverse and longitudinal waves
transverse — oscillate perpendicularly to the direction of energy transfer
ex . EM waves
Longitudinal — oscillate parallel to the direction of energy transfer
what waves can’t be polarised
longitudinal
what happens if you have two polarising filters at right angles of each other
no light will get through
how to tv and radio signals get polarised
there’s TV aerials that’s rods are all horizontal. this is so Tv signals are polarised by the orientation of the rods on the broadcasting aerial.
to receive strong signal, you have to line up rods on the receiving aerial with the rods on the transmitting aerial.
same for radio when you move the aerial around your signal will come and go as the transmitting and receiving aerials go in and out of phase
how is it proven that sunlight is made up of transverse waves
the reflected light has been partially polarised
only transverse waves can be polarised
explain how polaroid sunglasses help reduce glare caused by reflection
Polaroid material only transmits vibrations in one direction
reflected light mostly vibrates in one direction, so polaroid sunglasses filter that one direction, reducing glare
why can sound waves not be polarised
sound in longitudinal wave
vibrations are in same direction as energy transfer so it can’t be polarised
what is superposition
when two or more waves pass through each other
what’s the principle of superposition
when two or more waves cross, the resultant displacement equals the vector sum of the individual displacement
what’s interference
when two or more waves interfere
either destructive or constructive
trough and trough = bigger trough
trough and crest = zero
for destructive interference to be noticeable the opposing amplitudes need to be nearly equal
waves that are in phase have what in common
same displacement
same velocity
it means when the waves are at the same point in the wave cycle
or in sync
what’s the angles of phase and not in phase
in phase
0 or 360
out of phase
odd number multiples of 180
180
what does it mean to be coherent
two sources have to have
same wavelength
same frequency
fixed phase difference
what’s the formula for constructive interference and destructive interference path difference
constructive
path diff = n x wavelengths
destructive
path diff = ( n + 0.5 ) x wavelength
why is it hard to observe interference patterns in areas affected by two waves that are coherent
interference only is noticeable if amplitudes of the two waves are approximately equal
what’s a stationary wave
is the superposition of two progressive waves with the same frequency, moving in opposite directions
no energy is transmitted by a stationary wave
how do you detect stationary wave
setting up a driving oscillator at one end of a stretched string with the other end fixed. the wave generated by the oscillator will be reflected back and forth
what are nodes and antinodes
nodes are when amplitudes of the vibration is zero.
antinodes are points of maximum amplitude
what’s the first harmonic
it’s when the waves vibrates at the lowest possible resonant frequency
2 nodes and one antinodes
how can you demonstrate stationary waves with microwaves and sound
microwaves reflects off a metal plate making stationary waves
stationary sound waves are produced in the glass tube
the lycopodium powder laid along the bottom of the tube is shaken away
what’s a progressive wave
it’s a wave that carries energy from one place to another without transferring any material
what does the length, weight, and tension of string do to the resonant frequency experiment
( more l) the longer the string, the lower the resonant frequency
(more mu) the heavier the string, the lower the resonant frequency
(less tension) the losses the string the lower the resonant frequency because waves travel more slowly down a loose string
