Flashcards
Wave Motion
Cards in this deck (16)
- 1What is a progressive wave?A wave which transfers energy from one place to another through oscillations in a medium, but without altering the overall displacement of the medium
- 2State the two types of progressive waves and explain how they are different in terms of the oscillation of the mediumTransverse: oscillations are perpendicular to the direction of energy transfer
Longitudinal: oscillations are parallel to the direction of energy transfer - 3Give two examples of each type of progressive waveTransverse - Any two from: electromagnetic waves; secondary / shear waves (earthquakes); water waves; waves on stretched strings
Longitudinal - sound waves; primary / pressure waves (earthquakes) - 4Explain what is meant by the following terms: 1. Displacement 2. Amplitude 3. Wavelength 4. Period of oscillation 5. Frequency 6. Wave speed1. The distance of a particle from its equilibrium position - can be either positive or negative
2. The maximum displacement of the medium from its equilibrium position
3. The minimum distance between two points on the wave with the same displacement (points are perfectly in phase)
4. The time taken for a wave to complete one cycle / time taken for a complete wavelength to pass a particular point
5. The number of wavelengths which pass a particular point in one second / the number of complete oscillations which occur in one second
6. The distance travelled by the wave per unit time - 5Give the formula which links wave speed \(v\), frequency \(f\)/period \(T\) and wavelength \(\lambda\)\(v=f\lambda\)
\(vT=\lambda\) - 6What is the relationship between frequency \(f\) and period of oscillation \(T\)\[f=\frac{1}{T}\]
- 7What is a wave profile?A graph showing the displacement of all particles in the wave against the distance along the wave at a particular instant in time
Wave profiles are always shown as transverse as longitudinal waves are more complex to represent - 8Explain what is meant by phase differenceThe difference between the displacements of particles along a wave or the difference between the displacements of particles on different waves
OR
How far "out of sync / step" two points on a wave cycle are
Phase difference is measured in degrees or radians - 9Give two types of phase difference and their termsFor \(n \in \mathbb{Z}^+\)
Perfectly in phase: phase difference of \(2n\pi\) radians
Antiphase: phase difference of \((2n-1)\pi\) - 10What can displacement-time graphs be used to determine?Amplitude - maximum displacement in either direction
Period - time between two peaks/troughs or time between three adjacent points where the wave crosses the x-axis - 11How can frequency and amplitude be determined with an oscilloscope?Set the timebase to make it readable
Period is determined by the number of horizontal divisions x timebase - frequency = 1/period
Amplitude - measured in volts - height of the trace on the screeen, determined by half the number of vertical divisions between peak and trough x vertical sensitivity - 12Explain what is meant by: 1. Reflection 2. Refraction 3. Diffraction1. Waves change direction at a boundary between two different media, but remain in the same medium
2. Waves change direction at a boundary between two different media and pass through to the other boundary. There will be a partial reflection
3. Waves "spread out" when passing through a gap of a similar size to the wavelength or when passing near an edge - 13Explain what is meant by polarisationIf a wave causes the medium to oscillate in only one plane/direction, that wave is said to be plane-polarised. It can only happen to transverse waves as longitudinal waves are already plane polarised.
Unpolarised waves (where the medium oscillates in multiple directions/planes) can be plane polarised by passing them through a polarising filter - 14Define intensity of a waveAverage radiant power passing through a surface per unit area
\(I=\frac{P}{A}\) - 15How does intensity change with distance?\(I \propto \frac{1}{d^2}\)
\(I=\frac{1}{4\pi r^2}\) when wave source is treated as a pont - 16What happens to intensity when a polarised wave is passed through a polarising filter?Decreases to 0 when wave and filter are perpendicular
EXT: According to Mallus' Law:
\(I=I_0 cos^2{\theta}\) where \(\theta\) is the angle between the wave and the diffraction grating
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- A-level OCR Physics A-level (Topic 4 - Electrons, waves and photons) Flashcards on Wave Motion, created by James Norman on 30/05/2019.
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- James Norman
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