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23 Cards in this Set
- Front
- Back
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Phase Difference |
This is the fraction (difference) of a cycle between the vibrations of two vibrating particles, measured in either radians, degrees or fractions of a cycle |
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What can phase difference be measured in? |
Radians. Angles. Fractions of a cycle. |
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If a phase difference of two waves is 1/5 of a wavelength - how can you write this in radians and degrees? |
360 x 1/5 over 1 = answer in degrees 2 pie x 1/5 over 1 = answer in radians |
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What is meant by two waves not being in phase? |
There is no phase difference and the peaks all coincide at the same point |
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What is amplitude? |
The maximum displacement of a vibrating particle; for a transverse wave it is the distance from the middle (x axis) to the peak of the wave |
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What is wavelength? |
The distance between two adjacent vibrating particles (between two successive crests) |
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What is frequency? |
The number of cycles of a wave that pass a point per second |
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What is time period? |
The time taken for one oscillation |
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What are longitudinal waves? |
The partical displacement is parallel to the direction of wave propergation. The particles do not move along with the wave but only oscillate back and forth about their equilibrium position. These waves have compressions due to 'forward' movements. It has rarefractions caused by 'resverse' movement |
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What are transverse waves? |
Where the particle displacement is perpendicular to the direction of the wave propergation. The particles oscillate up and down about their equilibrium position as the wave passes by. |
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Example of longitudinal waves |
Sound waves Primary seismic waves |
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Example of transverse waves |
Electromagnetic waves Secondary seismic waves Waves that travel on a string |
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Example of longitudinal waves |
Sound waves Primary seismic waves |
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What Makes a mechanical wave? |
The wave propergates through a medium at a wave speed depending on the elastic or inertial properties of that medium. |
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How does a mechanical wave work? |
When the wave passes through a substance, the particles of the substance vibrates in a certain way which Makes nearby particles vibrate in the same way and so on |
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Examples of electromagnetic waves |
Radio, Micro, Infrared, Visible, Ultraviolet, X-rays, Gamma |
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What is special about the speed of EM waves? |
All EM waves travel at the same speed in a vacuum |
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What is a plane polarised wave? |
Transverse waves that vibrate in one plane only |
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What does unpolarised mean? |
That the vibrations of a wave change from one plane to another |
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Why would it matter if a radio receiver is aligned properly? |
Radio waves from a transmitter are polarised. The Aerial of a radio receiver needs to be aligned in the same plane as the radio waves to obtain the best reception |
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How does a polaroid filter work? |
A filter only allows through light which vibrates in a certain direction, according to the alignment of its molecules. This means the light that has passed through is in one plane. |
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What is cross polarisation? |
When two polaroid filters have been used one after the next and one polaroid is relative to the other. This creates a minimum light intensity as the polarised light from the first filter can't pass through the second filter as the alignment of molecules is at a 90 degrees. |
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What is special about electromagnetic waves being polarised? |
The plane of polarisation is defined as the plane in which the electric field oscillates. |
