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OCR Physics A G485 - Frontiers of Physics - 18th June 2015

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the equation of (change of lambda/lab lambda) = (velocity/speed of light) one, and probably the v=(lambda * frequency) one from last year

I presume this works for both if the source is moving and when the observer is moving? Also thanks.

Reply 1021

randlemcmurphy

This may be a really silly question but if the age of the universe is 1/H₀, and H₀ is a constant (the gradient of v/x graph) then how can the age of the universe ever change?

Reply 1022

L'Evil Fish

Original post by randlemcmurphy

This may be a really silly question but if the age of the universe is 1/H₀, and H₀ is a constant (the gradient of v/x graph) then how can the age of the universe ever change?

Because it isn't accurate

Galaxies will be around the line, not exactly on it

It's a line of best fit so, H0 is approximate

Reply 1023

actanide

Original post by SkilledNChilled

I presume this works for both if the source is moving and when the observer is moving? Also thanks.

I think you are making this way too complicated than it should be :wink:

technically speaking, our Galaxy is moving through universe just as other Galaxies are. Its about the change of the wavelenght between the one we observe here on earth and the one from distant galaxies. So yeah, both source and objects can be moving, but for the simplicity, you say that the receiver stays still and there is a change in wavelenght/frequency of the source

Reply 1024

actanide

Anyone done the specimen paper? I need help in question 4, I have no idea how to draw the graph of induced EMF.

Hate graphs.

Reply 1025

Engineering Lad

Original post by randlemcmurphy

This may be a really silly question but if the age of the universe is 1/H₀, and H₀ is a constant (the gradient of v/x graph) then how can the age of the universe ever change?

H0 is said to be constant, but really it should be called the 'Hubble nearly constant', since it's value is so uncertain. It's supposedly between 50 and 100 km/s/Mpc and normally we use a value of 70, which gives an age of approximately 13.7 billion years. This value changes depending on the value of H0 used within the given range.

Reply 1026

Raizel

https://86702370e68cc0f4d10e729b4f36a1fff6ecae1d.googledrive.com/host/0B1ZiqBksUHNYQzVrcE9IckMtcnM/January%202012%20QP%20-%20Unit%205%20OCR%20Physics%20A-level.pdf

6bii part 1
can someone explain to me the reason of that method of calculation to achieve the answer.

someone halp pls

Original post by actanide

I think you are making this way too complicated than it should be :wink:

Thanks!

Reply 1029

Elcor

I was way more prepared for G484 which makes absolutely no sense

Reply 1030

ETRC

Original post by actanide

someone halp pls

that was the most stupid question ever

Reply 1031

xy0mz

Could someone pls explain 9.(c) in June14, preferably with a diagram? Cheers. ImageUploadedByStudent Room1434540632.795327.jpg

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Reply 1032

Elcor

Was a complete waste of my time going into school

Reply 1033

sagar448

There are two medical tracers, technetium and FDG-18. I know FDG is used for PET but what is the technetium used for? Please help.

Reply 1034

actanide

Original post by ETRC

that was the most stupid question ever

i got something like this, do you reckon its correct?

Reply 1035

Alex621

Original post by Elcor

Was a complete waste of my time going into school

My teacher tried to make me go in today and he said 'we'll go through a past paper' and i told him i would go but i didn't bother in the end. I need to do all the past papers today and the time it would take me to get there didn't seem worth it especially considering we would probably spend the whole day on just one paper. :colonhash:

Reply 1036

actanide

Original post by sagar448

There are two medical tracers, technetium and FDG-18. I know FDG is used for PET but what is the technetium used for? Please help.

technetium is very transferrable around the body, mixed with glucose and other substances. It can be used to detect if a kidney is healthy. It goes through the kidney the same as water etc, and if the kidney is faulty, itll give off bigger radiation from that area, meaning the kidney doesnt pass liquids well

Reply 1037

Elcor

Original post by actanide

i got something like this, do you reckon its correct?

no it should be like a digital wave i.e. 2 horizontal lines

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Reply 1038

actanide

Original post by Elcor

no it should be like a digital wave i.e. 2 horizontal lines

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like this? or should it connect to the x-axis?

Reply 1039

Elcor

Original post by actanide

like this? or should it connect to the x-axis?

Yeah connected

It's because the rate of change of flux linkage is constant as the coil is moving at a constant velocity - hence constant e.m.f. induced

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