# Standing waves and phase difference

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Can someone please explain to me how standing waves work as well as phase difference. Thank you.

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#2

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Can someone please explain to me how standing waves work as well as phase difference. Thank you.

**Jennifer50**)Can someone please explain to me how standing waves work as well as phase difference. Thank you.

Phase difference is essentially how far through the wave cycle one wave/point along a wave is in comparison to another wave/point along the same wave. Those that are in phase (have a phase difference of 0°/0 rads) are at exactly the same point in the wave cycle, that is, they both have the exact same displacement as one another. Those that are in antiphase (have a phase difference of 180°/pi rads) and so when one point has maximum displacement, another has minimum displacement. For waves/points along a wave that have a phase difference of 90° or pi/2 rads) when one point has 0 displacement the other has a maximum displacement.

Hopefully this helps.

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Can you please explain this to me:I think it's called the 1st harmonic and I read that there is a second and third as well.

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#4

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Can you please explain this to me:I think it's called the 1st harmonic and I read that there is a second and third as well.

**Jennifer50**)Can you please explain this to me:I think it's called the 1st harmonic and I read that there is a second and third as well.

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#5

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Standing waves are formed when a progressive wave reflects off of a boundary and superposes with the incident wave to form a resultant wave with nodes and antinodes. Nodes are points along the stationary wave where the amplitude is 0 due to destructive interference whereas antinodes are points along the wave where the amplitude is at a maximum due to constructive interference.

Phase difference is essentially how far through the wave cycle one wave/point along a wave is in comparison to another wave/point along the same wave. Those that are in phase (have a phase difference of 0°/0 rads) are at exactly the same point in the wave cycle, that is, they both have the exact same displacement as one another. Those that are in antiphase (have a phase difference of 180°/pi rads) and so when one point has maximum displacement, another has minimum displacement. For waves/points along a wave that have a phase difference of 90° or pi/2 rads) when one point has 0 displacement the other has a maximum displacement.

Hopefully this helps.

**Jpw1097**)Standing waves are formed when a progressive wave reflects off of a boundary and superposes with the incident wave to form a resultant wave with nodes and antinodes. Nodes are points along the stationary wave where the amplitude is 0 due to destructive interference whereas antinodes are points along the wave where the amplitude is at a maximum due to constructive interference.

Phase difference is essentially how far through the wave cycle one wave/point along a wave is in comparison to another wave/point along the same wave. Those that are in phase (have a phase difference of 0°/0 rads) are at exactly the same point in the wave cycle, that is, they both have the exact same displacement as one another. Those that are in antiphase (have a phase difference of 180°/pi rads) and so when one point has maximum displacement, another has minimum displacement. For waves/points along a wave that have a phase difference of 90° or pi/2 rads) when one point has 0 displacement the other has a maximum displacement.

Hopefully this helps.

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#6

**Jennifer50**)

Can someone please explain to me how standing waves work as well as phase difference. Thank you.

Progressive waves are longitudinal or transverse waves which basically transfer energy from one point to another. For example any wave out of the electromagnetic spectrum is progressive (e.g. visible light transfers energy in the form of light).

Standing waves on the otherhand trap energy between two points. You also need to know how they are formed:

Progressive waves are initially formed, which would travel in opposite directions, and then be reflected off whatever is keeping the medium together and when they reflect back, they interfere and form "nodes" and "antinodes".

This might make it easier to understand:

Here, the vibrator would have a certain frequency, which would first form a progressvie wave. This wave would then be reflected off the pulley and the vibrator as it travels along the string. It then interferes constructively and destructively.

This is where "nodes" and "antinodes" come in.

Constructive interference = Antinode forms

Destructive interference = Node forms

A node is the minimum aplitude on a standing wave. Here, it would be the points where it seems like the string interceps, as the amplitude is zero.

An antinode is where the amplitude is maximum, which is the centre of the oval like shape formed, from the bottom to the very top.

If that doesnt really make sense, this should:

Also, a key difference is to remember that a standing wave has many amplitudes, whereas a progressive wave has only 1 amplitude which would be the max point. For example, on the standing wave any point between a node and antidnode is an amplitude but on a progressive wave these would just be points on the wave which have displacements.

Here's a comparison between the two:

Phase difference:

"The angle by which a wave lags or leads another"

Bascially, full wavelength has a phase difference of zero degrees (or 360 degrees) so it forms a full circle.

Try to remember that its all measured in angles relative to 360 degrees which is one full wavelength. So for example half a wvelength has a phase differnece of half of 360; 2 wavelengths would have a phase difference of two times 360...

Another thing to learn it the term "antiphase" which is when a trough and peak of two waves line up, e.g.:

On the left we see that two waves in phase (phase difference which is any amount of full wavlengths e.g. 360, 720 degrees) forms 1 wave which has a greater amplitude when they interfere which results in constructive interference.

On the right you can see that two waves which are in antiphase interfere destrucivel and from a wave with basically no amplitude.

I know my explanation is kind of hard to understand, but if you dont understand any points or have any other questions just let me know

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#7

(Original post by

(...)

A node is the

(...)

**derpz**)(...)

A node is the

**minimum amplitude**on a standing wave. Here, it would be the points where it seems like the string interceps, as the amplitude is zero.(...)

**maximum**point of a sinus curve, never as the minimum one.

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#8

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Sorry that I am nagging a bit about your explanation, but an amplitude is defined as the

**Kallisto**)Sorry that I am nagging a bit about your explanation, but an amplitude is defined as the

**maximum**point of a sinus curve, never as the minimum one."The maximum displacement from the undistrubed position", and in a progressive wave, there is only 1 point of maximum displacement (the peak/trough which have the same value just that one is negative).

I think I may have accidentaly written "minimum", but I definately meant maximum.

Thanks for correcting me there

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#9

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(...)

I think I may have accidentaly written "minimum", but I definately meant maximum.

Thanks for correcting me there

**derpz**)(...)

I think I may have accidentaly written "minimum", but I definately meant maximum.

Thanks for correcting me there

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#10

(Original post by

Fair enough. The rest of the explanation of yours is okay, but I must admit that I have never heard of an experiment set-up with a pulley, mass and vibrator when I was teached in standing waves.

**Kallisto**)Fair enough. The rest of the explanation of yours is okay, but I must admit that I have never heard of an experiment set-up with a pulley, mass and vibrator when I was teached in standing waves.

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#11

**Kallisto**)

Fair enough. The rest of the explanation of yours is okay, but I must admit that I have never heard of an experiment set-up with a pulley, mass and vibrator when I was

**teached**in standing waves.

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