3.1 progressive and stationary waves Flashcards
Define frequency and give its units
The number of waves passing through a point per second
(hertz) Hz
Define wavelength
The distance between 2 adjacent peaks on a wave
Define amplitude
The maximum displacement of a wave from its equilibrium position
How can you find the time period of a wave using its frequency?
T=1/f
What is phase difference and what is it measured in?
How much a particle/wave lags behind another particle/wave. Measured in radians , degrees or in fractions of a cycle
What is a longitudinal wave?
A wave of which oscillation of the particles is in the direction of energy transfer.
There are rarefractions (areas of low pressure)
There are compressions (areas of high pressure)
What is a transverse wave with examples?
Waves where the particle oscillations are perpendicular to the direction of energy transfer.
ie: electromagnetic waves
How fast do electromagnetic waves travel in a vacuum?
3x10^8 m/s speed of light
What ways do the magnetic and electric waves travel to each other?
They travel at right angles to each other
What does a polarising filter do?
Only allows oscillations in one plane
How is polarisation used as evidence of how transverse waves behave?
Polarisation can only happen if a waves oscillations are perpendicular to the direction of travel (as they are in transverse waves)
How is polarisation used in antennas ?
TV and radio signals are usually plane-polarised by the orientation of the transmitting aerial , so the receiving aerial must be aligned in the same plane of polarisation to receive the signal at full strength
What is a stationary wave ?
A wave which transfers no energy and whose positions of maximum and minimum amplitudes 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 ?
1) waves must be of the same frequency , wavelength and amplitude
2)They must travel in opposite directions
These conditions are often met when a wave is reflected back on itself
How are stationary waves produced?
A stationary wave is formed from the supersition of 2 progressive waves travelling in opposite directions along the same plane with the same frequency wavelength and amplitude
1) Where the waves meet in phase constructive interference occurs so antinodes are formed
2) Where the nodes meet completely out of phase destructive interference occurs and nodes are formed
Describe the first harmonic for a stationary wave with two closed ends
It consists of 2 nodes on either end and an antinode in the middle
Describe the second harmonic for a stationary wave with 1 closed end and one open end
Consists of 2 nodes and 2 antinodes with one node being at the close end and one antinode being at the open end
