3.1 - Progressive and stationary waves Flashcards
what is a progressive wave
transfers energy from one point to another without transferring the medium itself and the particles in the medium oscillate as the wave passes through them
define Amplitude
A wave’s maximum displacement from the equilibrium position
define frequency
The number of complete oscillations passing through a point per second
define wavelength
The length of one whole oscillation (e.g. the distance between successive peaks/troughs)
define speed
Distance travelled by the wave per unit time
How can you find out the time period of a wave using it frequency?
T = 1/f
what is a phaze
a fraction of a wave cycle
how far through the oscillation a point is
what is phase difference
the difference in phase between 2 points on a wave
what happens if two waves re half a wavelength apart
they are out of phase
what is phase difference measured in
radians and degrees
what is phase
on the same point on a wave
What is antiphase
opposite points on a wave
equation for wave speed
wave speed = frequency x wavelength
what is a longitudinal wave
A wave in which the oscillation of the particles is parallel to the direction of energy propagation.
what are the two components of a longitudinal wave
rarefactions ( areas of low pressure)
compressions (areas of high pressure)
what is a transverse wave
a wave in which oscillations occur perpendicular to the direction of energy propergation
example of a transverse wave
electromagnetic
water
what are mechanical waves
waves that require a medium to propagate
what is an electromagnetic wave
vibrating electric and magnetic fields that oscillate at right angles to each other
properties of electromagnetic waves
they can travel through a vacuum without a medium
and travel at the speed of light
what is unpolarised light
then the electric fields are oscillating in multiple planes
what happens if light is polarised
then the electric field is oscillating in one plane only
What does a polarising filter do?
causes plane polarisation by only allowing oscillations in one plane. and absorbing all other planes.
How is polarisation used as evidence of the nature of transverse waves?
Polarisation can only occur if a wave’s oscillations are perpendicular to its direction of travel (as they are in
transverse waves).
what happens when 2 polarising filters are placed at right angles to each other
no light will be transmitted through
what are the 3 uses of polarising filters
- reduces glare when photographing by absorbing some reflected light waves
- sunglasses
- TV aerials
How is polarisation used in antennas?
radio signals are 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.
how can a polarising filter be used to determine if a light is partially polarised
rotate the filter and observe if there is a change in light intensity which alternates every 90 degrees
why does light not pass through 2 polarised filters at right angles
as light first passes through polariser 1 it is plane-polarised in the vertical axis so all the horizonal wavelengths are absorbed, so when it then passes through polariser 2 the transmission axis is horizontal so wont allow light to pass trough
how does adding a third 45 degree filter alter the light intensity
after polariser 1 the light is vertically polarised but it has a component at 45 degrees which is able to pass through the polariser. This 45 degree wave also has a a component at 45 degrees so the wave is able to pass through the 90 degree polariser
what are stationary waves
A wave which transfers no energy and whose positions of maximum and minimum amplitude are constant.
what is a node
a point on a stationary wave where the displacement is 0
what is an antinode
a point on a stationary wave with maximum displacement
What are the conditions for a stationary wave to be produced?
● The waves must be of the same frequency, wavelength and amplitude.
● They must be travelling in opposite directions
when are the conditions for a stationary wave met
when a wave is reflected back on itself
what is superposition
the process when two waves combine into a single wave form when they overlap
the total displacement at a point is equal to the sum of the individual displacements at that point
what is constructive interference
