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

1. (Original post by OL1V3R)
Can someone explain to me why this radiation spectrum from the Sun has a wavelength of maximum intensity corresponding to blue light, when the Sun is orange? I don't understand this, could it be due to Doppler shift?
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That's a good question.
I dont think Doppler shift would be responsible for this, as radius of Earth's orbit is roughly constant (1 AU), so there is no relative motion between the Earth and the Sun, no shift.

What I could find:
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The sunlit sky appears blue because air scatters short-wavelength light more than longer wavelengths. Since blue light is at the short wavelength end of the visible spectrum, it is more strongly scattered in the atmosphere than long wavelength red light. The result is that the human eye perceives blue when looking toward parts of the sky other than the sun.[1] Near sunrise and sunset, most of the light we see comes in nearly tangent to the Earth's surface, so that the light's path through the atmosphere is so long that much of the blue and even green light is scattered out, leaving the sun rays and the clouds it illuminates red.

And:
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Light from the sun that does not happen to be traveling toward our eyes scatters off molecules and other small particles in the atmosphere. As previously explained, Rayleigh scattering is inversely proportional to the fourth power of wavelength, so that shorter wavelength violet and blue light will scatter more than the longer wavelengths of green and especially red light. Although the most strongly scattered wavelength of visible light in the sky is violet, limitations in the sensitivity of human eyes to shorter wavelengths of light means that the violet light in the sky is detected only weakly by our eyes. As a result, the sky is perceived as blue despite the fact that it is chiefly violet [3]. Conversely, glancing toward the sun, the colors that were not scattered away -- the longer wavelengths such as red and yellow light -- are visible, giving the sun itself a slightly yellowish hue. Viewed from outer space, the sky is black and the sun is white.

The reddening of sunlight is intensified when the sun is near the horizon, because the volume of air through which sunlight must pass is significantly greater than when the sun is high in the sky. Accordingly, the gradient from a red-yellow sun to the blue sky is considerably wider at sunrise and sunset.
http://en.wikipedia.org/wiki/Rayleigh_scattering

And the colors stated in the stellar classification are not very certain:
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Most stars are currently classified using the letters O, B, A, F, G, K and M, where O stars are the hottest and the letter sequence indicates successively cooler stars up to the coolest M class. According to an informal tradition, O stars are "blue", B "blue-white", A stars "white", F stars "yellow-white", G stars "yellow", K stars "orange", and M stars "red", even though the actual star colors perceived by an observer may deviate from these colors depending on visual conditions and individual stars observed. This non-alphabetical scheme has been developed from an earlier scheme using all letters from A to O, but the star classes were reordered to the current one when the connection to the star's temperature became clarified, and a few star classes were omitted as duplicate of others.
http://en.wikipedia.org/wiki/Stellar_classification
2. Guys is there going to be a session tommorow?
Can i download Elluminate now for tommorow's session is there is one or should it be right before the session?
3. What a shame, I missed the revision session (at work). Oh well.

The question topics on Windows Live are really useful! Thank you !
4. Hey guys, can anyone from here answer my topic? I realise now this thread was probably the better place to ask.

http://www.thestudentroom.co.uk/show....php?t=1315714
5. (Original post by OL1V3R)
I'll put the link up once I have the session ready, all you need to do is click on it and download the Java app, and you're in! It's very simple

I remember doing the Oxford Maths Admissions Test preparation sessions over Elluminate (I didn't host them, but went on a course of 5/6 sessions).

I will cover Nuclear Decay this session, and I could explain an extra little bit of maths that might be useful. Maybe if you want we can go through some astrophysics as well.

So this evening, I'm going to have a go at hosting one of these sessions and going through the Oscillations topic, not sure yet about going through any exam questions. If you have any questions though, feel free to let me know and maybe we can discuss them

The revision session will start at 5:00pm and here is the link. I'm not sure how long the session is going to last, since I've never hosted one before. Also bear in mind that content-wise my knowledge won't be perfect, so I'm in an equally modest position as you lot! I'll have a good stab at it though.

I'll do another one each evening. I'm also considering doing a few revision sessions for OCR Salters Chemistry (Unit F334).

I have missed the session, can you post the time for the next session earlier.
thanks
6. (Original post by Joann79)
Guys is there going to be a session tommorow?
Can i download Elluminate now for tommorow's session is there is one or should it be right before the session?
I think you should be able to download it now so you will be all set to go.I downloaded it like 1 hour before and I was able to go online

Cya today
7. (Original post by ishta)
I think you should be able to download it now so you will be all set to go.I downloaded it like 1 hour before and I was able to go online

Cya today
Is there one today?
How do you use it?
8. Have to do a thorough phy5 revision today.
9. (Original post by Pegasus92)
Is there one today?
How do you use it?

Ya should be at around 5 PM check back oliver will post the time.Go to the link that oliver posted and download the java applet and u are set to go
10. (Original post by ishta)
Ya should be at around 5 PM check back oliver will post the time.Go to the link that oliver posted and download the java applet and u are set to go
11. (Original post by Pegasus92)
Now you are ready you have to be online at the time oliver posts here
12. (Original post by ishta)
Now you are ready you have to be online at the time oliver posts here
Pm me when you get to know the time.
thanks
13. Guys, I'll be updating the times in this thread from now on (in the first post).
14. Does anyone have a copy of the formulae they give us in the exam for unit 5?

Thanks
15. (Original post by MattWT)
Does anyone have a copy of the formulae they give us in the exam for unit 5?

Thanks
It's there at the end of the syllabus, page 167.
16. In astrophysics, what do we need to know about Dark Matter? Im studying from the Miles Hudson book and its like less than half-a-page, and I dont get it the way they explain
17. (Original post by dimi3)
In astrophysics, what do we need to know about Dark Matter? Im studying from the Miles Hudson book and its like less than half-a-page, and I dont get it the way they explain
We dont need to know much anyway.
Just probably there is dark matter in the space, that represents about 90% of the Universe's mass.
As galaxies are spinning, they need some force to provide centripetal acceleration.
This force should be due to gravitational attraction, but the mass of the observed stars in those galaxies is not enough to cause that spinning speed (low mass => low force).
So there might be some 'dark matter' that has mass, but we didnt observe yet.
18. Did thermal physics yesterday
Oscillations today.
19. Unfortunately it turns out that because I don't have a Moderators' licence, I'm not able to record an Elluminate session for people to watch later It's because I'm only using a free 30-day trial which has some limited features.
20. Revision didn't go well as planned.

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