waves Flashcards
progressive waves
a progressive wave transfers energy without transferring material and is made up of particles of a medium oscillating
wavelength
the distance between adjacent points that oscillate in phase
amplitude
maximum displacement from peak to equilibrium position
frequency
the number of cycles per second
period
the time for one complete wave to pass a fixed point
displacement
distance and direction from its equilibrium position
cycle
once complete cycle is from maximum displacement to the next maximum displacement.
velocity
how fast the wave is travelling
Phase
difference
How much a particle/wave lags behind another particle/wave
longitudinal waves
made up of?
can they travell in a vaccum?
example?
oscillations are parallel to the direction of energy transfer
made up of compressions and rarefractions
they cannot travel in a vaccum
sound waves
sound waves
type of wave?
direction?
regions of…
can be demonstrated by?
longitudinal
air molecules oscillate parallel to the direction of propagation
regions of high and low pressure travel through the air
can be demonstrated by pushing a slinky horizontally
transverse waves
example?
oscillations are perpendicular to the direction of energy transfer
electromagnetic waves
electromagnetic waves
consist of…
they all travel..
consist of oscillating electric fields and magnetic fields. neither can exist without eachother
they all travel at the same speed in a vaccum 3x10^8
if the electromagnetic wave is POLARISED…
electric field oscillates in one plane only
if the electromagnetic wave is UNPOLARISED…
electric field oscillates in multiple planes
polarising filter-
what does it do?
2 polarising filters?
it absorbs one component of the electric field and transmits the other
2 polarising filters at right angles would absorb both components so no light is transmitted.
what is polarisation evidence for?
why?
evidence for the nature of transverse waves
because polarisation can only occur if a waves oscillations are perpendicular to its direction of travel
application of polarisation:
polaroid sunglasses
Polaroid sunglasses are an application of polarisation. They reduce glare by blocking partially
polarised light reflected from water and tarmac, as they only allow oscillations in the plane of the
filter, making it easier to see.
application of polarisation:
TV and Radio signals
usually plane-polarised by
the orientation of the rods on the transmitting aerial, so the receiving aerial must be aligned in the
same plane of polarisation to receive the signal at full strength.
superposition
t
where the displacements of two waves are combined as they pass each other,
the resultant displacement is the vector sum of each wave’s displacement.
what are the two types of interference that can occur during superposition?
when do they occur?
Constructive interference occurs when 2 waves have displacement in the same
direction
● Destructive interference occurs when one wave has positive displacement and the other
has negative displacement, if the waves have equal but opposite displacements, total
destructive interference occurs
how is a stationary wave formed?
energy transfer?
A stationary wave is formed from the superposition of 2 progressive waves, travelling in
opposite directions in the same plane, with the same frequency, wavelength and amplitude.
no energy is transferred by a stationary wave
antinodes
when are they formed?
regions of maximum amplitude
when the waves meet in phase constructive interference occurs so antinodes are formed
nodes
when are they formed
regions of no displacement
when the waves meet completely out of phase, destructive interference occurs and nodes are formed
1st harmonic
double frequency?
lowest frequency at which a stationary wave forms.
double the first harmonic frequency to find second harmonic frequency
what is the distance between adjacent nodes?
half a wavelength
formation of a stationary wave-A string fixed at one end, and fixed to a driving oscillator at the other
A wave travelling down the string from the oscillator will be reflected at the fixed end of the
string, and travel back along the string causing superposition of the two
waves, and because the waves have the same wavelength, frequency
and amplitude, a stationary wave is formed
stationary waves-microwaves
how are they formed?
finding nodes and antinodes?
the waves are reflected to a metal plate and are superposed with waves travelling in opposite direction.
to find the nodes and antinodes use a microwave probe.
stationary waves- sound waves
what produces them?
how?distance between each node?
a loudspeaker produces stationary soundwaves in a glass tube with powder.
the powder laid along the bottom of the tube is shaken away from the antinodes but left undisturbed at the nodes. the distance between each node is half a wavelength and the frequency of the signal generator is known so by c=fλ
the speed of sound in air can be found.
what does a point source produce?
produces circular wavefronts. this source produces waves of a single frequency/wavelength
path difference
difference in the distance travelled by 2 waves
what are the conditions for coherence?
a coherent light source will have the same frequency and wavelength and a fixed phase difference
constructive interference
when does it take place?
path difference?
amplitude signal?
if the waves arrive at a certain point in phase then constructive interference will take place.
the path difference to this point will be equal to a whole number of wavelengths.
large amplitude signal
destructive interference
when does it take place?
path difference?
if the waves arrive at a certain point in antiphase then destructive interference takes place.
this will happen when the path difference.
