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The Physics PHYA2 thread! 5th June 2013

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Original post by ahmad94
Hey, this is the paper I am dreading the most. I only need approx 40 out of 70 to get an A overall, but i am struggling to get there.

Anyone have any idea what might come up so I can go over it a bit. It's my only hope.


No one can predict unfortunately. This is because same questions always come year after year. All they do is change the diagram, the quantity and the wordings. Do as many past papers as you can. 40 marks should not be hard to get for you. Good luck! :smile:
Any ideas what the 6 marker may be on? It was on waves in January.
Thank you both! Yeah NedStark I noticed that which is why I was so surprised at the markscheme. Not really sure the appropriate way of thanking on the tsr- if there is a tag button or something but thanksssss
Also Ahmad94 you may have already seen this but http://www.aqa.org.uk/exams-administration/about-results/uniform-mark-scale/convert-marks-to-ums shows that in the unit 2 paper raw marks gain more ums on average than in the unit 1 paper, so maybe you don't even need 40! x
Original post by IWantSomeMushu
Any ideas what the 6 marker may be on? It was on waves in January.


Just revise everything! They could repeat waves again. who knows?:biggrin:
Original post by StalkeR47
No one can predict unfortunately. This is because same questions always come year after year. All they do is change the diagram, the quantity and the wordings. Do as many past papers as you can. 40 marks should not be hard to get for you. Good luck! :smile:


Do you remember on the Unit 1 thread? Everyone was predicting what the 6 marker was on. No one. Not even one person guessed particles. What a gift. (I dropped marks on it as well :angry:)
Original post by NedStark
Do you remember on the Unit 1 thread? Everyone was predicting what the 6 marker was on. No one. Not even one person guessed particles. What a gift. (I dropped marks on it as well :angry:)


Oh yes! You are right! I think I only dropped about 1 mark. And it was so easy (a gift like you said). I hope we get 6 marker as easy as unit 1 on unit 2. :smile:
Original post by NedStark
Do you remember on the Unit 1 thread? Everyone was predicting what the 6 marker was on. No one. Not even one person guessed particles. What a gift. (I dropped marks on it as well :angry:)


I hope it's not on another area of waves then because I'm bad at it lol.

I think I may have dropped one mark on the Unit 1 6-marker.
What affects the angle in diffraction gating?


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Original post by Jimmy20002012
What affects the angle in diffraction gating?


Posted from TSR Mobile


The slit spacing and the wavelength of the light beam because dsin theta=n lambda.
Original post by StalkeR47
The slit spacing and the wavelength of the light beam because dsin theta=n lambda.


And how exactly does each one affect the angle?

Also if you have many slits would you have much sharper and further apart maxima?


Posted from TSR Mobile
Original post by Jimmy20002012
And how exactly does each one affect the angle?

Also if you have many slits would you have much sharper and further apart maxima?


Posted from TSR Mobile


Rearrange the equation to get sin theta(let x be theta and y be lambda). dsinx=ny, sinx=ny/d (this is where d is the slit spacing and n is the order of peak). so, from this equation, you can see decreasing the wavelength decreases the angle(x). Also, decreasing the slit spacing (d) increases the angle(x). So, if you have many slits, you will get more diffraction (more fringes would appear on the screen). Having more slits does not effects the fringe spacing. Further, dsinx=ny does not have the quantity to deal with fringe spacing. So, use w=yD/s (w is the fringe spacing). From this equation, you can see increasing the wavelength increases the fringe spacing. Also, increasing the distance between the slits and the screen (D) increases the fringe spacing (min max further apart) and finally, increasing the slit spacing (s) decreases the fringe spacing. How about that much of a details m8?:smile:
Original post by Jimmy20002012
And how exactly does each one affect the angle?

Also if you have many slits would you have much sharper and further apart maxima?


Posted from TSR Mobile


And yes, the advantage of the diffraction grating (having many slits) makes the fringes much sharper only. :smile:
(edited 10 years ago)
Original post by StalkeR47
Rearrange the equation to get sin theta(let x be theta and y be lambda). dsinx=ny, sinx=ny/d (this is where d is the slit spacing and n is the order of peak). so, from this equation, you can see decreasing the wavelength decreases the angle(x). Also, decreasing the slit spacing (d) increases the angle(x). So, if you have many slits, you will get more diffraction (more fringes would appear on the screen). Having more slits does not effects the fringe spacing. Further, dsinx=ny does not have the quantity to deal with fringe spacing. So, use w=yD/s (w is the fringe spacing). From this equation, you can see increasing the wavelength increases the fringe spacing. Also, increasing the distance between the slits and the screen (D) increases the fringe spacing (min max further apart) and finally, increasing the slit spacing (s) decreases the fringe spacing. How about that much of a details m8?:smile:


Thanks so much :biggrin: Also during diffraction grating does the central maximum have zero path difference due to the wave arriving in phase, as well as the the first order as you would have exactly 1 wavelength so path difference would equal 1, thus having a path difference of 1. Am I right?

When do you get waves in anti phase in diffraction gating?


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Original post by Jimmy20002012
Thanks so much :biggrin: Also during diffraction grating does the central maximum have zero path difference due to the wave arriving in phase, as well as the the first order as you would have exactly 1 wavelength so path difference would equal 1, thus having a path difference of 1. Am I right?

When do you get waves in anti phase in diffraction gating?


Posted from TSR Mobile


I think you do not really need to know that much details for the AS-level specification. I am not sure about the second question.:confused:
Original post by Jimmy20002012
Thanks so much :biggrin: Also during diffraction grating does the central maximum have zero path difference due to the wave arriving in phase, as well as the the first order as you would have exactly 1 wavelength so path difference would equal 1, thus having a path difference of 1. Am I right?

When do you get waves in anti phase in diffraction gating?


Posted from TSR Mobile


at your zero order you get zero path difference, at your first order(s) [bright fringes] your path difference is nλ n \lambda where n n is an integer this also means that the phase difference is a multiple of 2π 2 \pi.

where you get [dark fringes] between say zero and the first order or first and second order, the path difference is (n+12)λ (n + \frac{1}{2}) \lambda where the phase difference is a multiple of π \pi (for it to be perfectly out of phase)
(edited 10 years ago)
Original post by x-Sophie-x
Now, I'm very confused haha
o.O

I thought there was wave diffraction, and particle diffraction.
And particle diffraction is electron diffraction? No?
And wavefronts occur with wave diffraction only?


Now I'm utterly confused..
what is electron diffraction? I've never seen that before..(Panic mode.)
Original post by Currentlysmilin
Now I'm utterly confused..
what is electron diffraction? I've never seen that before..(Panic mode.)


An electron can act as a wave too and diffract, you can find it's wavelength using the de broglie wavelength formula,
lambda = h/mv

... but I don't think you need to know it for this unit :tongue:
can someone tell me the different instances where i may be asked to calculate the frequency of a wave and how i would do it? thanks! this is the only topic i'm really struggling with!
Original post by PickwickianGeek
can someone tell me the different instances where i may be asked to calculate the frequency of a wave and how i would do it? thanks! this is the only topic i'm really struggling with!


speed of light = frequency times wavelength. You do not need to worry about the different instances. It is more likely to be in the wave topic. You only need to know speed of light (3.0x10^8ms-1) and the wavelength which will be given in the question somehow.
this word document is SO useful, pretty much goes through EVERYTHING for PHYA2 ... can't attach it here because file too big, but for anyone struggling or just wants to look at notes .. seriously check this out :biggrin::

http://getrevising.co.uk/resources/mechanics_materials_and_waves_phya2_revision

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