stationary waves Flashcards
how are stationary waves produced?
standing (stationary waves) are produced by the superposition of two progressive waves of the same frequency, wavelength and amplitude travelling in opposite directions
how is the formation of a stationary wave achieved?
by a travelling progressive wave being reflected
state the difference between stationary waves and progressive waves in terms of energy
stationary waves store energy whereas progressive waves transfer energy.
explain, in terms of interference, what happens to stationary waves upon formation using a graph of displacement against position
- at the start of cycle, waves interfere destructively (zero displacement)
- 1/4 cycle later, waves overlap and interfere constructively (the stationary waves amplitude is 2x therefore - peak then trough)
- 1/2 cycle, waves interfere destructively (zero displacement)
3/4 cycle, waves overlap and interfere constructively (amplitude 2x, trough peak)
briefly describe how you would demonstrate the formation of stationary waves
setting up a driving oscillator at one end of a stretched string with the other end fixed
the wave generated by the oscillator is reflected back and forth and
compare progressive and stationary waves in terms of amplitude
progressive waves - all points have the same amplitude in turns therefore
stationary waves - each point has a different amplitude depending on the amount of superposition
compare progressive and stationary waves in terms of wavelength
progressive - points exactly a wavelength apart are in phase, the phase of points of about one wavelength vary from 0-360 degrees
stationary - points between nodes are in phase. points on either side of a node are out of phase
compare progressive and stationary waves in terms of nodes/antinodes
progressive waves do not have nodes/antinodes whereas stationary waves do
compare progressive and stationary waves in terms of wavespeed
progressive waves - the wavespeed is the speed at which the wave moves through a medium
stationary waves -
compare progressive and stationary waves in terms of wavespeed
progressive waves - the wavespeed is the speed at which the wave moves through a medium
stationary waves - each point of a wave oscillates at a different speed. the overall wave does not moves
what is a stationary wave made up of
it is a transverse wave (each particle vibrates at right angles to the string) and has nodes and antinodes
what are nodes?
nodes are points on the wave where the amplitude of the vibration is zero
what are antinodes?
antinodes are points on the wave where the vibrations are at their maximum amplitude
why do nodes and antinodes do not moves on the string?
Nodes are fixed and antinodes only move in the vertical direction
what is the phase difference of a stationary wave?
The phase difference between two points on a stationary wave are either in phase or out of phase Points between nodes are in phase with each other
Points that have an odd number of nodes between them are out of phase
Points that have an even number of nodes between them are in phase
what type of interference occurs at a node?
the waves are in antiphase therefore total destructive interference because the displacements of the two waves canacel eachother out always
what type of interference occurs at an antinode?
the waves are in phase so constructive interference because the displacements of the two waves combine to make a bigger displacement
how can you calculate the wavelength of a stationary wave?
number of loops / 2
explain how you would demonstrate stationary waves through microwaves
a microwave source is placed in between a metal plate and small detector between the two. the microwave source is reflected at the metal plate.
The reflector can be moved to and from the source to vary the stationary wave pattern formed, the superposition of the wabe and its reflection produces a stationary wave.
by moving the detector between the transmitter and reflecting plate, you can find the nodes (minima) and antinodes (maxima) of the stationary wave pattern
explain how you would demonstrate stationary waves through sound waves
stationary waves are formed inside an air column, which is how insturments such as clarinets and organs work therefore
This can be demonstrated by placing a fine powder inside the air column and a loudspeaker at the open end
At certain frequencies, the powder forms evenly spaced heaps along the tube, showing where there is zero disturbance as a result of the nodes of the stationary wave
to produce a stationary wave there must be a minima (node) at one end and a maxima (antinode) at the end with the loudspeaker
what is the distance between each pile of powder (node)
wavelength / 2
what is the speed of sound equivalent to?
c = f x lambda therefore c = f x 2d = 2df
