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AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread]

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Bumping in hope someone sees.

When talking about discharge tubes, during the discovery of electrons, some revision notes say they are produced through thermionic emission from the cathode, but others say the electrons come from the low pressure gas in the tubes being ionised due to the high potential difference, releasing electrons in the process.

Which is correct and in which context are they needed?

This is in turning points.
Original post by saad97
Thanks, could you quickly go over hydrogen balmer absorption lines and how they are produced in the spectrum of a star please? I was confused by that question :/


I have no idea, all I know is the occur in the classes B and A, and are cause when electrons excite from the level n=2

Praying they don't come up
Reply 2342
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a.a.k
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Original post by Adangu
Sorry to bother but can someone help me with 1biii) and 1ci) please? http://filestore.aqa.org.uk/subjects/AQA-PHYA51-QP-JUN14.PDF


1biii use E=mc^2
take E from part before it

1ci its just N-Z graph
Can someone list the size of wavelengths in order.... I mean radio, uv, etc...
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CD223
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Original post by Sbarron
Can someone list the size of wavelengths in order.... I mean radio, uv, etc...


In order of decreasing wavelength...

Radio
Micro
Infrared
Visible
UV
X Ray
Gamma


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Original post by betbi3etwerrd
Which text book is this.

Also can someone explain to me the significance of critical mass during nuclear fission.


The CGP one,

also the critical mass is the amount of fissile material needed in order for a reaction to continue on at a steady rate
Good luck everyone


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Original post by AR_95
Just a note

Ionisation Chambers, and Radiation monitoring could also come up tomorrow


Ionisation chambers? Do you mean for testing the properties of different radiation modes?
Original post by Gome44
I have no idea, all I know is the occur in the classes B and A, and are cause when electrons excite from the level n=2

Praying they don't come up


I'm praying quite a lot of the stuff doesn't come up tbh :frown:
Original post by CD223
In order of decreasing wavelength...

Radio
Micro
Infrared
Visible
UV
X Ray
Gamma


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Thanks, thought so just couldn't remember infa red/micro cheers
Original post by ricardomontoya97
In a way, I want all of you to fail to bring the boundaries down. Sorry, not sorry.


You shouldn't have to rely on others as well as luck. Work hard and create your own luck

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Reply 2351
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Original post by jackcros
Bumping in hope someone sees.

When talking about discharge tubes, during the discovery of electrons, some revision notes say they are produced through thermionic emission from the cathode, but others say the electrons come from the low pressure gas in the tubes being ionised due to the high potential difference, releasing electrons in the process.

Which is correct and in which context are they needed?

This is in turning points.


This is what i think.

Electrons released from thermionic emission are accelerated though high pd. The electrin collide low pressre gas atoms which become excited. when desxcited teh emit photons (thats why they glow). Some electrons escape the atom so atoms are ionised and positivily charge therefore attract electrons again this way pd is created.

i am not sure about this is this right?
Original post by CD223
In order of decreasing wavelength...

Radio
Micro
Infrared
Visible
UV
X Ray
Gamma


Posted from TSR Mobile


Hi, something happened to the previous 6 markers on the first page. It show s a blank page. Do you mind fixing it please, I'm really desperate.
Original post by a.a.k


The truth is its not whats right, its what the exam board want. As far as they are concerened its definitely under the line.
Original post by Dante991
You shouldn't have to rely on others as well as luck. Work hard and create your own luck

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Obviously I have been working but still doesn't mean I couldn't do with some extra help :wink: A* here I come
What are some points on the stability curve (Z against N) that remembering them will help.
Hey can someone help me? Basically, in the June 2011 paper, the question about binding energy for fission you took into account the neutrons but in the June 2014 paper they gave the binding energy of each element and you werent supposed to take into account neutrons. Why is that? Thank you!
Original post by Specter
Hey can someone help me? Basically, in the June 2011 paper, the question about binding energy for fission you took into account the neutrons but in the June 2014 paper they gave the binding energy of each element and you werent supposed to take into account neutrons. Why is that? Thank you!


With june 2014 it says per nucleon. So that is a proton or a neutron. So it would be 235 x 7.59.
Original post by palaseum9
Turning points 6 marker preductions??

Turning points - Previous 6 markers:
June 14' - TEM microscopes
June 13' - Hertz radio waves experiment (with stationary waves context)
June 12' - Wave-particle duality of light
June 11' - Double Slit experiment (with reference to Newton's and Huygen's theory of light)
June 10' - STM microscopes


it wont be microscopes, that makes me very happy
Any predictions for 6 marker? Or things they might ask in detail about what havent been asked before like damping in unit 4

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