AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread]

Jealous. Sounds like I went to the wrong college


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Probably it's pretty weird to hear people talking about picking where they want to go for sixth form though like what I can only get to one place (the glory of rural areas). It is a very good college but that's just a coincidence really, I go there because it's our college?

Kinda the same with me really. People travel miles to get to my college (not because it's rural, but because like 4,000 people go there and it has a good reputation) but it's only a 10 minute walk away for me haha!


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Yeah we get a lot of people travelling a long way for our college as well like I didn't even realise it had a good reputation until I was here I had no choice realistically. Like people leave the private schools in the same town to come here instead sometimes. Bit further than a ten minute walk though! (even my grandparent's is a 25 minute walk, we're about a 15 minute drive depending on traffic. Which for me getting to college is 5 minutes car, 10 minutes park and ride because it's a lot cheaper and on the way to work for mum anyway).

Ah it does seem pretty local still!
What do you happen to know about a Cassegrain reflector?

Cassegrain reflectors have the secondary mirror directly opposite the primary mirror, reflecting light back through a hole in the primary mirror to an eyepiece, whereas Newtonian reflectors have an angled mirror to reflect light to an eyepiece in the side of the telescope. Basically just a case of where the eyepiece is I think!

Ah thank you! My teacher talked of Newtonian reflectors today - he set us a research task on Cassegrain reflectors. Do both types of reflecting telescopes block out parts of the image by using a secondary convex mirror?

They both have a secondary convex mirror, but our teacher was talking about how they don't block out the image as such (there's not a black blob in the middle) because light comes into the telescope from all directions or the region lost (due to that and the hole in the secondary mirror on Cassegrains) is insignificant or something, it just decreases the amount of light getting in.

I need as many notes as I can for astrophysics, it's hard to take in all those keywords.

How far into it are you?
We've done very little. Basically everything past resolving power in lenses is still to come :/


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Oh right!
So why would you use a cassegrain over a Newtonian or vice versa?


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We learned drawing lens diagram, resolving power, distance in parsec, different telescopes (I forgot all of them), chromatic and spherical aberration, Wien's displacement law, Stefan's law, magnitudes, star classes, etc.
I have the CGP book at least, might it help?

I have no clue... the Newtonian would likely put the eyepiece in a more convenient place for actual observing but I can't think of any other reasons and I don't have any in my notes?

Haha yeah the CGP book is good do you have the AQA textbook too?


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Unfortunately no, we only have the one for the compulsory parts (no options A-D), and that's the part I really need.

Ah right! I'll try and PM you the Astro AQA notes when I can


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Thanks.

Oh right! I'm not sure how much of this research task is just for interest and how much is actual facts we need to recall... Thanks anyway!!


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