AQA Physics PHYA5 - 28th June 2016 [Exam Discussion Thread] Watch

Protoxylic
Badges: 14
Rep:
?
#181
Report 2 years ago
#181
(Original post by Abc321zxc)
Michelson–Morley experiment

Main aim -> Prove that an aether exists. The aether is a postulated medium through which light travels and so if such an aether exists the speed of light in an observer's frame depends on the relative speed of the observer to this aether.
Result -> Ironically they proved that an aether doesn't exist and thus the speed of light is constant for any observer in any frame of reference and is equal to 3x10^8m/s
Method:
Use a diffractometer consisting of a semisilvered mirror angled at 45, a laser consisting of coherent and monochromatic light is incident on this mirror, approx half of the intensity goes through and travels to a mirror, half reflects up (90 degrees to the straight through beam) and heads towards another mirror which is the same distance away as the the other mirror is to the semi-silvered mirror. The laser beams meet up again at the semi-silvered mirror after reflecting off the mirrors, reflect down to an observing scope and a diffraction pattern is observed.
The diffraction pattern depends on the optical path difference between the straight through beam and the reflected beam and if such an aether exists then the beam travelling parallel to the aether (i.e parallel to the earth orbit direction) will have a different path length to the perpendicular beam. Thus we expect upon rotation of the apparatus by 90 degrees for the path lengths to swap and thus a shift in diffraction pattern. This wasn't observed; there was no change in diffraction pattern. Hence disproving the existence of an aether -> verify c is constant.

(It's hard to describe the apparatus in words, but I'm sure you know what it looks like and can translate my explanation to it)
1
quote
reply
Dann_a
Badges: 2
Rep:
?
#182
Report 2 years ago
#182
(Original post by Protoxylic)
Link the question, I did this exam last year so I don't quite remember questions from specific papers
http://filestore.aqa.org.uk/subjects...W-QP-JUN10.PDF

http://filestore.aqa.org.uk/subjects...W-MS-JUN10.PDF
0
quote
reply
Protoxylic
Badges: 14
Rep:
?
#183
Report 2 years ago
#183
If you're referring to Q1. Changes in absolute temperature are numerically equivalent to the changes in temperature measured in Celsius.
Spoiler:
Show
T(k)=T(c)+273
T(k2)-T(k1)=[T(c2)+273]-[T(c1)+273]=T(c2)-T(c1)

Where k=kelvin, c=celsius
It's nothing more than a translation in the scale so whether or not you use K or C for deltaT is arbitrary. Although the units are strictly in kelvin
0
quote
reply
boyyo
Badges: 6
Rep:
?
#184
Report 2 years ago
#184
(Original post by aksdj)
power= E/t
W= J/s
and the activity is the number of nuclei that decay per second so the unit would be s^-1
J*s^-1= W so P=AE

Have you ever done a question where you've had to use it?
0
quote
reply
particlestudent
Badges: 12
Rep:
?
#185
Report 2 years ago
#185
Do you guys perform better on your Unit 5 papers or Unit 4?
0
quote
reply
Mattematics
Badges: 5
Rep:
?
#186
Report 2 years ago
#186
Could somebody explain why the second option is incorrect?



I thought proper time was the shortest time and that it was the time experienced by the object experiencing both events. Surely therefore the time in the muon's frame of reference will be shorter than the observers, ergo time passes more slowly for the observer?
0
quote
reply
Protoxylic
Badges: 14
Rep:
?
#187
Report 2 years ago
#187
(Original post by Mattematics)
Could somebody explain why the second option is incorrect?



I thought proper time was the shortest time and that it was the time experienced by the object experiencing both events. Surely therefore the time in the muon's frame of reference will be shorter than the observers, ergo time passes more slowly for the observer?
You are misunderstanding the term 'shortest time'. The frame of reference that experiences proper time experiences the shortest time interval. So for every tick in the muon frame, less time has elapsed than for every tick in the observer/rest frame.
0
quote
reply
aksdj
Badges: 1
Rep:
?
#188
Report 2 years ago
#188
How do they make this paper hard? I feel like it is more to do with memorising than U4 does anyone have some hard questions they could ask us
0
quote
reply
ssel17
Badges: 1
Rep:
?
#189
Report 2 years ago
#189
(Original post by Protoxylic)
Proper time is defined as the frame that experiences the smallest possible time interval and is the frame for which the person/thing/object is present at both events. E.g a muon travelling between points A and B is present in it's own frame at the origin at both points A and B and thus the muon and it's frame experience proper time - all other time intervals are longer including the observer. So in this case the muon experiences proper time.

The protons experience proper time and also a contracted length for points A and B defined as the edges of the detector, i.e the detector length is shorter in their frame compared to the lab frame.
So basically, in the frame of reference of the muons, the time would be the proper time?

Whilst in the frame of reference of the protons, the protons distance is the contracted distance, not the proper distance?

If that's correct, I think I have got my head around it.
0
quote
reply
AQATrolledMe
Badges: 2
Rep:
?
#190
Report 2 years ago
#190
(Original post by aksdj)
How do they make this paper hard? I feel like it is more to do with memorising than U4 does anyone have some hard questions they could ask us
Do you think they may ask us about stellar evolution ?
0
quote
reply
Protoxylic
Badges: 14
Rep:
?
#191
Report 2 years ago
#191
(Original post by ssel17)
So basically, in the frame of reference of the muons, the time would be the proper time?

Whilst in the frame of reference of the protons, the protons distance is the contracted distance, not the proper distance?

If that's correct, I think I have got my head around it.
That is correct
0
quote
reply
ssel17
Badges: 1
Rep:
?
#192
Report 2 years ago
#192
(Original post by Protoxylic)
That is correct
Thank you, much appreciated.
0
quote
reply
Franckenstar
Badges: 2
Rep:
?
#193
Report 2 years ago
#193
(Original post by particlestudent)
Do you guys perform better on your Unit 5 papers or Unit 4?
lol with the applied physics part in section B I think I prefer section A
0
quote
reply
aksdj
Badges: 1
Rep:
?
#194
Report 2 years ago
#194
(Original post by boyyo)
Have you ever done a question where you've had to use it?
Not so far but I haven't done much for this one so wouldn't know if it could come up :s
0
quote
reply
aksdj
Badges: 1
Rep:
?
#195
Report 2 years ago
#195
(Original post by AQATrolledMe)
Do you think they may ask us about stellar evolution ?
Maybe, tbh in astro I'm more worried about the Wein's and Stefan's law stuff :/
0
quote
reply
Mango Milkshake
Badges: 2
Rep:
?
#196
Report 2 years ago
#196
5C applied physics is so hard :cry:
0
quote
reply
Euclidean
Badges: 10
Rep:
?
#197
Report Thread starter 2 years ago
#197
(Original post by Mango Milkshake)
5C applied physics is so hard :cry:
I'm dreading it...
0
quote
reply
kother2015
Badges: 2
Rep:
?
#198
Report 2 years ago
#198
Can someone please help with qs 4c on section A ? How do we know that more time would be spent below 25 degrees?!
Thanks
0
quote
reply
Mango Milkshake
Badges: 2
Rep:
?
#199
Report 2 years ago
#199
(Original post by Euclidean)
I'm dreading it...
Are you doing it too?

My teacher didn't even know any of it, he said I have to self teach it all. Have no resources either. :shot:
0
quote
reply
Euclidean
Badges: 10
Rep:
?
#200
Report Thread starter 2 years ago
#200
(Original post by Mango Milkshake)
Are you doing it too?

My teacher didn't even know any of it, he said I have to self teach it all. Have no resources either. :shot:
Yeah I'm in the same boat. Self teaching and I can't find any good resources

The part I dread most is the COP stuff, it's very hit and miss at the moment for me
0
quote
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

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.

Personalise

University open days

  • University of Lincoln
    Mini Open Day at the Brayford Campus Undergraduate
    Wed, 19 Dec '18
  • University of East Anglia
    UEA Mini Open Day Undergraduate
    Fri, 4 Jan '19
  • Bournemouth University
    Undergraduate Mini Open Day Undergraduate
    Wed, 9 Jan '19

Were you ever put in isolation at school?

Yes (282)
27.35%
No (749)
72.65%

Watched Threads

View All