You are Here: Home >< Physics

# Waves Phase difference URGENT HELP PLEASE Watch

Announcements

1. I've been sitting here for a very long time attempting to answer the questions but I cannot. For question 1a) I answered 'the air particles vibrate parallel to the direction of the wave propogation'. For part b) I don't know what is different...
And question 2 is hard! The phase difference between point 0 and A, I put down as 135 degrees but it doesn't seem like it's 135 degrees and I have no clue how to do it...and for part b I put down 3/8 of a wavelength which is 3cm since the question states the whole wavelength is 8cm. But is this correct?
Can someone please help me out? I have done research and I am stuck and I have no answers to these questions! Thank you soooo much...
2. (Original post by CounTolstoy)

I've been sitting here for a very long time attempting to answer the questions but I cannot. For question 1a) I answered 'the air particles vibrate parallel to the direction of the wave propogation'. For part b) I don't know what is different...
And question 2 is hard! The phase difference between point 0 and A, I put down as 135 degrees but it doesn't seem like it's 135 degrees and I have no clue how to do it...and for part b I put down 3/8 of a wavelength which is 3cm since the question states the whole wavelength is 8cm. But is this correct?
Can someone please help me out? I have done research and I am stuck and I have no answers to these questions! Thank you soooo much...
section 1 - looks like points A and B are separated by about 1/2 a wavelength... you could confirm with a ruler. since a full wavelength is 360 degrees that would mean they have a phase difference of 360/2 degrees i.e. 180 degrees and what that means is that particles at those points have the same magnitude of displacement at the same instant but in opposite directions (which you can also confirm with a ruler on the first graph)
Since they've both got the same amplitude and frequency you can also say that *at the same instant* they have the same speed (but in opposite directions) and the same magnitude of acceleration (but accelerating in opposite directions)
3. (Original post by Joinedup)
section 1 - looks like points A and B are separated by about 1/2 a wavelength... you could confirm with a ruler. since a full wavelength is 360 degrees that would mean they have a phase difference of 360/2 degrees i.e. 180 degrees and what that means is that particles at those points have the same magnitude of displacement at the same instant but in opposite directions (which you can also confirm with a ruler on the first graph)
Since they've both got the same amplitude and frequency you can also say that *at the same instant* they have the same speed (but in opposite directions) and the same magnitude of acceleration (but accelerating in opposite directions)
But how are points 0 and A 180 degrees out of phase as point A is not parallel to point 0 on the axis?
4. (Original post by CounTolstoy)
But how are points 0 and A 180 degrees out of phase as point A is not parallel to point 0 on the axis?
well at 180 they should be the same distance from the axis on opposite sides*... & that's what it looks like from here

360 is 1 wavelength which is the distance from a peak to the next peak (or trough to trough)
180 is 1/2 a wavelength (or the distance horizontally between a peak and the next trough)
points that are 360 degrees of phase apart are the same distance and direction from the axis **

* this is also the explanation for standing wave nodes & destructive inteference
** this is also the explanation for standing wave antinodes & constructive interference.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: October 1, 2016
Today on TSR

### How would you do in an Oxford interview?

Put yourself through the test

### STI without any sexual activity?

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.