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# Unit 2 Physics Edexcel!! HELP! :( Watch

1. I don't understand this wth?
First they say that the wavelength is in phase. then they say its not
Does that even make sense? I'm starting to give up on Unit 2. Serious.

I've attached the question with the thread btw.
2. (Original post by PenguinsAreAwesome)

I don't understand this wth?
First they say that the wavelength is in phase. then they say its not
Does that even make sense? I'm starting to give up on Unit 2. Serious.

I've attached the question with the thread btw.
There is a difference between phase and path difference.
-They are saying the waves are in phase so they are in the same point of the wave cycle. E.g at highest amplitude.
- The waves just have a difference in length of journey in wavelengths.

In this question they are saying that one wave started 90 degrees before the other one. Seeing as 1 wavelength is 360 degrees, 90 degrees must be 1/4 of a wavelength. So that is the path difference.

Does this make sense? If not just say and I'll try to draw a picture or something Feel free to ask me any questions, I am a Year 13 physics student. xoxox
3. (Original post by EyesSetToKill)
There is a difference between phase and path difference.
-They are saying the waves are in phase so they are in the same point of the wave cycle. E.g at highest amplitude.
- The waves just have a difference in length of journey in wavelengths.

In this question they are saying that one wave started 90 degrees before the other one. Seeing as 1 wavelength is 360 degrees, 90 degrees must be 1/4 of a wavelength. So that is the path difference.

Does this make sense? If not just say and I'll try to draw a picture or something Feel free to ask me any questions, I am a Year 13 physics student. xoxox
Thankyouu so so so much !

You're awesome
4. The waves are lambda in phase when they leave the light source.

But when they reach the screen they have travelled different distances (hence different path differences) and so are now out of phase.
5. (Original post by PenguinsAreAwesome)
Thankyouu so so so much !

You're awesome
I'm glad I could help!
Good luck on Friday xoxox
6. Any predictions what might come tomorrow??
7. Hopefully little on electricity and more on the particle model and interference etc.
8. (Original post by Liver2029)
Hopefully little on electricity and more on the particle model and interference etc.
Yay! I hopee soo!
9. I hope there isn't much Photoelectric effect because they always seem to ask really difficult questions on it!!!!
10. (Original post by EyesSetToKill)
I hope there isn't much Photoelectric effect because they always seem to ask really difficult questions on it!!!!
hahah the paper was seriously bull**** ! how was yours ?
11. (Original post by PenguinsAreAwesome)
hahah the paper was seriously bull**** ! how was yours ?
I found it ok actually. Only difficult question was the last one on emf (I am guessing that it is the A/A* question). However it was a retake and I am currently doing A2 physics which has more electricity in so I guess I know a bit more.

The year 12s I did it with seemed to absolutely hate it. The guy next to me just gave up like 1hr into the exam... :/

I'm sure you did well though!!!

Updated: May 28, 2012
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