fuzzybear
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#261
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what are you all using to revise your optional topics?

I feel like I don't have enough resources for astrophysics
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JRP95
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#262
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(Original post by fuzzybear)
what are you all using to revise your optional topics?

I feel like I don't have enough resources for astrophysics
Collins aqa student support book for astrophysics, thats all you need then just do the past paper questions.
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Seb Hudson
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#263
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#263
(Original post by JRP95)
Collins aqa student support book for astrophysics, thats all you need then just do the past paper questions.
I just can't seem to be able to remember the lens stuff because it's SO boring! Any ideas on how to learn it?
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amish123
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#264
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#264
(Original post by Seb Hudson)
I just can't seem to be able to remember the lens stuff because it's SO boring! Any ideas on how to learn it?
Do you mean when it comes to drawing ray diagrams or the more detailed stuff such as resolving power and Rayleigh Criterion? I can help with you with both


(Original post by fuzzybear)
what are you all using to revise your optional topics?

I feel like I don't have enough resources for astrophysics
http://www.antonine-education.co.uk/...trophysics.htm

This is a very useful source which helped me to understand most of the topic.
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JRP95
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(Original post by amish123)
Do you mean when it comes to drawing ray diagrams or the more detailed stuff such as resolving power and Rayleigh Criterion? I can help with you with both
.
Am I missing something because resolving power and Rayleigh criterion are not complicated from what I've read (just one formula and then like one line to memorise/learn for both)
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Seb Hudson
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(Original post by amish123)
Do you mean when it comes to drawing ray diagrams or the more detailed stuff such as resolving power and Rayleigh Criterion? I can help with you with both
I'm okay with the ray diagrams I believe, its just focal points when you're given the magnification and stuff, I never work out what exactly you're supposed to do Thanks!
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smith50
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Any more revision material on Turning points anyone?
Smith
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amish123
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(Original post by JRP95)
Am I missing something because resolving power and Rayleigh criterion are not complicated from what I've read (just one formula and then like one line to memorise/learn for both)
No it's not that difficult to learn. It's just knowing when to apply the Rayleigh Criterion equation (lambda/d) when it comes to comparing the performance of different telescopes. For example, in order for a radio telescope to have the same resolving power as a standard reflecting optical telescope, the diameter of the dish of the radio telescope needs to be much larger because the wavelength of radio waves (~1cm to 1m) is much longer than that of visible light (~550nm).

Make sure you know the definitions of Rayleigh Criterion and also that of what an Airy Disc is.

(Original post by Seb Hudson)
I'm okay with the ray diagrams I believe, its just focal points when you're given the magnification and stuff, I never work out what exactly you're supposed to do Thanks!
Ah right I see, I struggled at first with recognising what they're actually asking you to do. It's just simple 'tricks' you need to learn, such as the angular magnification, M, is given by alpha/beta (the angles subtended at different points). But this is also the same as fo/fe (the focal length of the objective lens and eyepiece lens respectively). Think about what different values you have been given in a question, what values you can work out, and then how you can finally arrive at an answer.
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Technetium
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(Original post by smith50)
Any more revision material on Turning points anyone?
Smith
Have you had a read through this?: http://filestore.aqa.org.uk/subjects...W-TRB-OGTP.PDF
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smith50
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(Original post by Technetium)
Have you had a read through this?: http://filestore.aqa.org.uk/subjects...W-TRB-OGTP.PDF
Will do
Smith
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fuzzybear
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anyone got the collins student support book?

for astrophysics, (specifically binary star system), I'm having a real headache over this example question in the book on page 90:



Surely the tangental velocity (i.e the actual speed at which the stars are moving) would be different for each of the stars, so how can you get one single figure for velocity. I don't get this. They're each moving in their own orbits which are different sizes, and if the time taken (time period) to complete their respective orbits is the same, then surely the speed at which they're moving must be different....

secondly, why does that equation give you the distance between the two stars. Somehow it shows that 'r' (radius of 'circular motion) equals the distance between the two stars, It just doesn't make sense to me at all, how am I suppose to visualize this :confused:
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amish123
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(Original post by fuzzybear)
anyone got the collins student support book?

for astrophysics, (specifically binary star system), I'm having a real headache over this example question in the book on page 90:



Surely the tangental velocity (i.e the actual speed at which the stars are moving) would be different for each of the stars, so how can you get one single figure for velocity. I don't get this. They're each moving in their own orbits which are different sizes, and if the time taken (time period) to complete their respective orbits is the same, then surely the speed at which they're moving must be different....

secondly, why does that equation give you the distance between the two stars. Somehow it shows that 'r' (radius of 'circular motion) equals the distance between the two stars, It just doesn't make sense to me at all, how am I suppose to visualize this :confused:
You're correct, the tangential velocities of the two stars would be different, however because this is A Level Physics, we make assumptions and here we are assumuing that a smaller star is orbiting a bigger star, the bigger star acting as a centre of mass. Funnily, I was actually watching a lecture on binary star systems yesterday, take a look at the link below (Walter Lewin is a genius may I add).

http://ocw.mit.edu/courses/physics/8...es/lecture-23/
Forward to 20:49

As for your second question, I think this is to do with the fact that you're assuming that you are in the same plane of the orbit of this binary system. Maybe these pictures may clear things up:
Name:  eclipsing_binary.gif
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Name:  algol.gif
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Size:  19.5 KB

If you look at the second picture, the radius of orbit of the smaller star is the same as the distance between both stars.

Hope I've helped you!
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fuzzybear
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(Original post by amish123)
You're correct, the tangential velocities of the two stars would be different, however because this is A Level Physics, we make assumptions and here we are assumuing that a smaller star is orbiting a bigger star, the bigger star acting as a centre of mass. Funnily, I was actually watching a lecture on binary star systems yesterday, take a look at the link below (Walter Lewin is a genius may I add).

http://ocw.mit.edu/courses/physics/8...es/lecture-23/
Forward to 20:49

As for your second question, I think this is to do with the fact that you're assuming that you are in the same plane of the orbit of this binary system. Maybe these pictures may clear things up:
Name:  eclipsing_binary.gif
Views: 169
Size:  5.8 KB
Name:  algol.gif
Views: 192
Size:  19.5 KB

If you look at the second picture, the radius of orbit of the smaller star is the same as the distance between both stars.

Hope I've helped you!
Thanks

So in that example question I posted, one of the star is basically not moving? and this is the reason why we would get only one tangential velocity?

I've looked at the animation you provided, is that suppose to represent my example question?
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amish123
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#274
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(Original post by fuzzybear)
Thanks

So in that example question I posted, one of the star is basically not moving? and this is the reason why we would get only one tangential velocity?

I've looked at the animation you provided, is that suppose to represent my example question?
That seems like it is the case for this question yes. Yep, I think the animation depicts what is going on in the question you've provided. Rest assured, if a question involving Doppler Shift does appear in our exam, I'm sure they'll make the wording of the question much clearer to understand.
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iwantopas19
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#275
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hey can someone please help me in unit 4???

how do we know the direction of a particle in bubble chamber or such? I have no idea to find the field or the direction of force..can someone please help me with it...??
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Einsteinium
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#276
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Does Anyone have notes for astronomy?


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JayJay95
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#277
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Hi everyone, hope revision's going well!
Was just wondering if anyone could tell me the experiments that we need to know for the exam (astrophysics too please) would be really helpful.

Thanks! :top:
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jethacan
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Can anyone doing astrophysics help me with this question?
I'm stuck on (b)(ii) but I can do the rest.

Name:  Astro question.jpg
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I tried looking at the mark scheme and I couldn't understand it at all :/
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jarasta
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I thought we made a mistake picking Applied physics, but wow. Astro and Turning points seems much harder.:P
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ehtisham_1
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Turning points is f u c k I n hard, especially the special relativity and considering our teacher can't explain it makes it worse

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