Waves Flashcards
Define frequency and give its units
Number of waves passing through a point per Second measured in Hz
Define wavelength
Distance Between two adjacent peaks or troughs on a wave
Define Amplitude
The maximum displacement of a wave from its equilibrium position
What is time period
Number of seconds for the wave to cycle 1 wavelength
1/ frequency
What is Phase Difference
What fraction of a cycle are two points stationed away from each other
measured in radians
What is a longitudinal wave?
A wave in which direction of the particles is parallel to the energy transfer
There are rare fractions (areas of low pressure) and compression (areas of high pressure)
What is a Transverse Wave
Waves where the direction of the particles is perpendicular to energy transfer
Em waves
In a EM wave how are the electric and magnetic fields arranged
Perpendicularly
What does a polarising filter do?
Only allows oscillations in a specific plane by restricting the vibrations to a specific direction
How is polarisation used as an evidence of the nature of transverse waves?
Polarisation can only occur if a waves oscillations are perpendicular to the direction of travel
As longitudinal waves would be able to pass through any polarisation filter.
How is polarisation used in antennas?
Tv and radio signals are usually plane polarised by the orientation of the rods on the broadcasting aerial.
So the Receiving aerial must be alined in the same way to receive the signal at full strength
What is a stationary wave?
A wave which transfers no energy and whose position of maximum and minimum amplitude (antinodes) & nodes are constant
Caused by the interference between 2 identical progressive waves traveling in opposite directions
Each particle doesn’t experience the entire amplitude of the wave
What is a node?
A point on a stationary wave where the displacement is 0
What is an anti node?
A point on a stationary wave of maximum magnitude of displacement
What are the conditions for a stationary wave to exist?
Waves must be of same
- frequency
- wave length
- amplitude
Must be travelling in opposite directions
Often met when a wave is reflected back on its self
How are stationary waves produced?
- Formed from the superposition of 2 progressive waves traveling in opposite directions with he same frequency, wavelength and amplitude
-Waves form antinodes of maximum displacement when two are met in phase, due to constructive interference
-Waves form fixed position nodes when the two meet completely out of phase, due to destructive interference
Describe the first harmonic for a stationary wave with two closed ends
2 Nodes at either end with an anti node in the middle
Describe the second harmonic for a stationary wave with 1 closed end and 1 open end
2 anti nodes and 3 nodes
1 Node in the middle
2 nodes at each end
Anti nodes stationed half way between eahc node
What is the formula for anti nodes and nodes
where n = number of harmonic
Number of Antinodes = n
Number of nodes = (n+1)
What is a Progressive wave?
- A wave that transfers Energy outside of a system
-Waves which are not confined to a system - Each particle experiences the entire amplitude of the wave
What is an Oscilloscope?
A device which plots the signal of a voltage supply and shows how it varies over time.
How do an Oscilloscope work? ( 5 steps)
1) Electron gun is aimed at a fluorescent screen
2) 2 Y-Plates are positioned either side of the beam
3) 2 X plates are positioned either side of the beam perpendicular to y plates
4) when the potential difference of the chosen supply is applied across either of the plates electrons path are displaced towards the positive of the plates
5) the higher the potential difference the higher the electrons are displaced, and greater distance away from the centre of the fluorescent screen. This is then plotted on the graph.
RMs Voltage =
Voltage peak * 2^(-1/2)
What is the formula you need the calculate the wavelength of nth harmonic of a stationary wave?
What is the formula you need the calculate the frequency of nth harmonic of a stationary wave?
What is the formula that is used to workout the tension in a string within a stationary wave?
(in formula book)
What is the phase difference of two particles in the stationary wave that:
Have the same direction towards the Equilibrium Position?
Have opposite directions towards the Equilibrium Position?
1) In-Phase 0 or 2Pi
2) Counter Phase Pi
How do you predict the way a particles going to move in a stationary wave?
Look at the particle left of your chosen one.
Your particle will mimic this
What is Path Difference
Number of wavelengths in terms of displacement between two points
Signal strength goes through a series of max and minimum points
at certain distances the direct and reflected waves interfere constructively to produce a maximum signal and interfere destructive to create a minimum signal
This is due to the phase difference between the reflected and direct waves changing periodically as distance to x decreases.
How do you prove that diffraction will occur for a specific slit gap
1) calculate de Broglie wavelength
2) use diffraction equation Sin(x) = landa/slit spacing to calculate first order
3) if this gives a viable answer if wavelength is smaller then gap
4) Then yes diffraction would be observable if the wavelength and split spacing are in the same magnitude
How do you calculate Mass per unit length
Density of metal * cross sectional area in m^3 x 1m
Explain why the first harmonic calculation for a wire at high tensions produces frequencies higher then expected
Wire could neck/ thin at parts if the tension is very large causing a lower mass per unit length, making the frequency produced higher then expected.
