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# Edexcel A2 Physics Unit 5 'Physics from Creation to Collapse' watch

1. Have to do a lot of work tomorrow.
2. I don't really understand Oliver's pdf on Astrophysics...
3. (Original post by Doughboy)
I don't really understand Oliver's pdf on Astrophysics...
Were you there for yesterdays session?
4. (Original post by Doughboy)
I don't really understand Oliver's pdf on Astrophysics...
The 'life cycle of stars' part is a bit messy , it's definitely better to hear what he's saying while drawing.
The 'life cycle of stars' part is a bit messy , it's definitely better to hear what he's saying while drawing.
If you want, I can put up a cleaner diagram of the life cycle of stars...
6. (Original post by OL1V3R)
If you want, I can put up a cleaner diagram of the life cycle of stars...
Oh, it's fine for me, I remember it from yesterday.
Maybe somebody else wants it.
7. No I wasn't at his session yesterday. Was forced to do Biology. I have to go out today at about 1800 hrs so I might miss today's session as well -_-

But I have good news about 6PH04. It's quite possible that I got a high B/low A
8. (Original post by Doughboy)
No I wasn't at his session yesterday. Was forced to do Biology. I have to go out today at about 1800 hrs so I might miss today's session as well -_-

But I have good news about 6PH04. It's quite possible that I got a high B/low A
And I might get a high A
9. I don't what I'll get, but it will be something greater than a B.
10. Hey guys, got an Astrophysics question. One of my books says you can deduce the radius of main sequence stars and their distance away by three measurements;

1) Ensure that the star's spectrum tells you that it is a main sequence star
2) Measure the peak wavelength in the star's wavelength
3) Measure the radiation flux from the star

But I'm confused with the first point - Ensure that the star's spectrum tells you that it is a main sequence star - How do they deduce this, what property of their spectrum tells you it is a main sequence star? Is it that ONLY main sequence stars are black-body radiators and thus their spectrum covers all wavelengths of electromagnetic radiations - And that white dwarfs and red giants/supergiants are thus not black bodies?

I tried recording my session earlier today and when I pressed "stop" on the software and tried saving it, it wouldn't work and it didn't save the file!

However if someone wants to add me on MSN we can just chat about the topics covered.
12. (Original post by Sasukekun)
Hey guys, got an Astrophysics question. One of my books says you can deduce the radius of main sequence stars and their distance away by three measurements;

1) Ensure that the star's spectrum tells you that it is a main sequence star
2) Measure the peak wavelength in the star's wavelength
3) Measure the radiation flux from the star

But I'm confused with the first point - Ensure that the star's spectrum tells you that it is a main sequence star - How do they deduce this, what property of their spectrum tells you it is a main sequence star? Is it that ONLY main sequence stars are black-body radiators and thus their spectrum covers all wavelengths of electromagnetic radiations - And that white dwarfs and red giants/supergiants are thus not black bodies?
All stars behave as black body radiators.

I think that's because we can check what particular elements are there on the spectrum, hence we know what elements the star consists of.
And as we know it's mostly hydrogen and helium for the stars on the main sequence, the spectrum with absorption lines at hydrogen would come from a main sequence star.

Yeah, this explanation is not very clear, but..
13. Let me explain this

1- Dispersing the light from a star to produce a spectrum
2- We can measure the peak wavelength
3- from it we can calculate the surface temperature
4- Now if that surface temperature is ON THE MAIN SEQUENCE it is on the main sequence rite?

if not it IS NOT ON MAIN SEQUENCE rite?
14. (Original post by darkibm)
Let me explain this

1- Dispersing the light from a star to produce a spectrum
2- We can measure the peak wavelength
3- from it we can calculate the surface temperature
4- Now if that surface temperature is ON THE MAIN SEQUENCE it is on the main sequence rite?

if not it IS NOT ON MAIN SEQUENCE rite?
Ok, here's the diagram:

Observed ƛmax = 322nm, which corresponds to 9000K.
Is it Procyon B (white dwarf), Sirius (main sequence star) or Deneb (supergiant)?
15. Just wondering, how much Unit 1 and 2 stuff would come up, seeing as it's said to have synoptic elements.
and my teacher said Unit 1/2 stuff might be on it.
This exam scares me.
16. (Original post by DrDé)
Just wondering, how much Unit 1 and 2 stuff would come up, seeing as it's said to have synoptic elements.
and my teacher said Unit 1/2 stuff might be on it.
This exam scares me.
I think for this paper it's just the Unit 5 content. You need to know the basics of Units 1 and 2 for Unit 5 anyway, but is it really worth learning the whole AS Waves topic all over again?
17. (Original post by OL1V3R)
I think for this paper it's just the Unit 5 content. You need to know the basics of Units 1 and 2 for Unit 5 anyway, but is it really worth learning the whole AS Waves topic all over again?
Yeah, just the basics of springs (oscillations), electricity (electric heater => thermal energy), waves (red shift) etc.
We will be provided with the formulae sheet anyway.
Simples.
18. Thanks guys,
I'm not going to go over Materials and Waves again. No point really.
19. http://ephysics.physics.ucla.edu/phy...bodylarge.html
Might be usefull.
20. Thanks to whoever uploaded all those hundreds of questions on all the topics ! They've been really useful.

I've been putting them together in a way that means the marks add up to 80, so I sit it like a mock test and get some kind of idea of what I might realistically get. They're just random questions picked out of those documents, so they add up to 80 marks.

I'll share the rest of them tomorrow if people want more. At school so only have one of them atm.
Attached Files
21. madeuptest1.docx (35.4 KB, 493 views)

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