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

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Does anyone mind showing me how this would look please?


Mark scheme doesn't have an image to check against
Untitled.pngHey can anyone help me with this. Basically why is the answer to 1c 'Objective because as m=fo/fe so for magnification fo>fe'

Following that explanation, isnt it dependant on the focal length of the other eyepiece used so if you had a lens of focal length was 80cm wouldnt you use that as the objective. How can they ask us which one is the objective if they dont give us any details about what would be used as the eyepiece? Thanks so much

Oops that pic cuts the last line, but you can see the main part of the question.
(edited 8 years ago)
hi, could someone help with core 2014 question 1b ii. I know its a simple question im just getting myself confused, just not sure how to deal with the neutrons either side, thanks!

http://filestore.aqa.org.uk/subjects/AQA-PHYA51-QP-JUN14.PDF
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Original post by RobHunter97
Does anyone mind showing me how this would look please?


Mark scheme doesn't have an image to check against


Diverging lenses aren't even on the spec. Where did you get that paper?


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Original post by CD223
Diverging lenses aren't even on the spec. Where did you get that paper?


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Medical Physics section of the June 2010 paper
Unit 5B
(edited 8 years ago)
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Original post by Specter
Untitled.pngHey can anyone help me with this. Basically why is the answer to 1c 'Objective because as m=fo/fe so for magnification fo>fe'

Following that explanation, isnt it dependant on the focal length of the other eyepiece used so if you had a lens of focal length was 80cm wouldnt you use that as the objective. How can they ask us which one is the objective if they dont give us any details about what would be used as the eyepiece? Thanks so much

Oops that pic cuts the last line, but you can see the main part of the question.


I know what you mean, the question isn't nice. Only think I can think of is in terms of ratios for the distances given.

For magnification the focal length of the objective has to be much greater than that of the eyepiece - for a telescope in normal adjustment the ratio of fo:fe should be about 5:1 when drawing diagrams for three non axial rays.

Given the distances considered, it wouldn't be feasible for the lens of focal length ~70cm to be the eyepiece as this would mean an objective is needed that has a focal length of approximately ~350cm for the same sharp image to be produced when the telescope is in normal adjustment.

Given the distances mentioned (200cm between screen and object), it makes more sense that the lens is used as the objective, as this would mean that the eyepiece only needs a focal length of ~14cm.

If you think that the length of the telescope is fo + fe as well, then a telescope of length 84cm in normal adjustment sounds more sensible than one of 420cm for this application.

I can't think of another way of explaining it - I totally agree that it's not a nice question though. I tripped up on it too and wasn't happy with the mark scheme.


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Original post by RobHunter97
Medical Physics section of the June 2010 paper
Unit 5B


Sorry! I mistook it for Astro - do ignore me - we only deal with converging!



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Original post by CD223
Sorry! I mistook it for Astro - do ignore me - we only deal with converging!



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No worries :smile: Hoping somebody knows. I think I'm right, but the fact it's a diverging lens makes me think I've done it wrong
Why does an alpha particle cause more ionisation that a beta particle of the same initial kinetic energy?
Original post by CD223
Diverging lenses aren't even on the spec. Where did you get that paper?


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I'm after the answer to this too, so stupid that they basically just say 'diagram drawn correctly' for full marks...

I drew horizontal line from tip of object to lens line, then projected it back onto the focal point BEFORE the lens, then drew another line from tip of object to the point of intersection of the axes and drew the image where these two lines intersected, between -F and lens axis
Original post by gcsestuff
Is this the general idea of the inversion tube experiment:

Lead spheres are heated to a certain temperature.

They are then put in a tube and the tube is rotated a certain number of time.

Due to energy loss from gravity, mgh and the total no. Of rotations we can say that mcT=mghn

Which cancels to give us c= gln/T


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Do we need to know how to measure it using electrical methods aswell ?
Original post by Sumz.96
Why does an alpha particle cause more ionisation that a beta particle of the same initial kinetic energy?


Charge of an alpha particle is greater in magnitude (think it's 2e) where as a Beta is just 1
Original post by Sumz.96
Why does an alpha particle cause more ionisation that a beta particle of the same initial kinetic energy?


Because it has more momentum and would 'knock' another atoms particles more of a distance (I think thats basically ionising) Its also much larger in size so way more likely to hit another atom
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Original post by Sumz.96
Why does an alpha particle cause more ionisation that a beta particle of the same initial kinetic energy?


Alpha particles have a greater mass. For the same kinetic energy this means their speed must be slower.

This means that there is a greater probability of collisions with molecules, ionising them by stripping them of outer electrons.


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Is an assumption of the change of state of matter that this happens at a constant mass? In other words, there is no mass lost when a liquid is vaporised?


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Original post by AR_95
Charge of an alpha particle is greater in magnitude (think it's 2e) where as a Beta is just 1


Original post by kevincarreira
Because it has more momentum and would 'knock' another atoms particles more of a distance (I think thats basically ionising) Its also much larger in size so way more likely to hit another atom


Original post by CD223
Alpha particles have a greater mass. For the same kinetic energy this means their speed must be slower.

This means that there is a greater probability of collisions with molecules, ionising them by stripping them of outer electrons.


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Thank you!
Original post by CD223
Is an assumption of the change of state of matter that this happens at a constant mass? In other words, there is no mass lost when a liquid is vaporised?


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Yes, I think so, if mass was lost then you're losing energy as well
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q1.png

Q4 (c). June 2011. Why is the temperature higher and not lower? MS doesn't make sense to me that much :/
So charge has nothing to do with the fact that alpha is more ionising then Beta?

Isn't Alpha positive 2 charge, so more likely to attract the electrons out of the atom it collides with if we put aside momentum for now
Original post by CD223
q1.png

Q4 (c). June 2011. Why is the temperature higher and not lower? MS doesn't make sense to me that much :/


It's exposed to a higher temperature so I think it gains more energy

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