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OCR A - Cosmology June 2008 How did it go ?

MSNBOY

11

i thought it was ok got some weird answers the last question threw me off. but otherwise i hope i get a C

Reply 1

abc1234

Not bad, I guess I just got lucky with the questions.

Reply 2

The_Professor

Was pretty easy I thought! We were very lucky with the last question, as synoptic questions can be horrible sometimes...and this one was pretty easy!
For the graph showing absorption of atmosphere against wavelength, did you do visible light or ultraviolet light when naming the radiation of letters?

Also for long thought experiment, did you do effect of Gravity on time or effect on light?

Reply 3

abc1234

Gravity effect on visible light I think, can't say it's "easy" though things have a strange tendancy of going wrong when I say that lol.
Not sure which question you mean there.

Reply 4

username138327

1

Was alrite. Didn't particularly like the last one but then I was in a bit of a rush coz I kept losing concentration due to stoopid general studies in the morning...

Reply 5

The_Professor

abc1234

Gravity effect on visible light I think, can't say it's "easy" though things have a strange tendancy of going wrong when I say that lol.
Not sure which question you mean there.

Ye I thought it was that first, so I described how light is curved, but then I realised that was wrong. It said frequency of light, so I think it meant the one where time changes and clocks tick slowly in gravity fields.

Reply 6

abc1234

lol I just blagged it

Reply 7

VAI2007

1

I did the clocks are slow in strong gravity thing.

I thought it went suprisingly well. The last question was shockingly okay!

I got ?? x10^41 for ther mass of the galaxy
1445pcs for the distance to that star
1.17m for the heigh of the fountain
around half an hour (2969s?) for the next to last question.

Reply 8

andysmith25

10

I put UV for that, as it was right on the edge.
And for the thought experiment, I did a light source which was accelerating - you get a Doppler shift kind of thing, as it's accelerating towards the wavefronts, so wavelength decreases and frequency increases, then gravity is equivalent to acceleration.

Overall I thought it was quite easy, but the first exam in ages that I haven't had spare time at the end. I left the height of fountain question and came back to it later. I was just putting the figures into E=mgh when we were talked to put pens down - argh!

I did that :biggrin:

aa

(edited 12 years ago)

Reply 11

bob_blob

Im a nuclear one,
but for the synoptic question i got about 1.17m or 1.18m for the height of the fountain and I got the sameish efficiency.......

Reply 12

username138327

1

VAI2007

I did the clocks are slow in strong gravity thing.

I thought it went suprisingly well. The last question was shockingly okay!

I got ?? x10^41 for ther mass of the galaxy
1445pcs for the distance to that star
1.17m for the heigh of the fountain
around half an hour (2969s?) for the next to last question.

Got the same for all but the distance to the star. Can't remember what I got but it was defo 3 figs....

Reply 13

royale_sufi

I found it okay you know... but the height thing took me a bit of time to get only to forget to put the efficiency of 35% into my calculation... aww well i should only lose a mark.

One weird question was that one question where they asked you why the power reaching the surface of the Earth was only 1000W and not 1400W at the equator... and they also asked you why the power delivered decreases as you move from the north to the south poles of the equator... i think i dont mine wrong but i was just talking about the atmosphere and how it is different at different places and more light will be reflected... was i right??

and for the first part of the 20 mark question part C) i) did you guys get 60W from multiplying the intensity by the area???

Reply 14

daltervia

I got something round 398 pc for that distance question... oh I dunno.
That thought experiment question sucked - hopefully I did stuff about effect on gravity on light - hopefully I'll get a mark for talking about the equivilence principle.

I did get 60W, then somehing like 4.2W

what did people get the radial velocity and why it wasn't close to c?

Reply 15

Jacka

royale_sufi

One weird question was that one question where they asked you why the power reaching the surface of the Earth was only 1000W and not 1400W at the equator...

It was 1400W in the outer atmosphere and 1000W on the surface, so you needed to put about how the light would be absorbed or reflected.

Reply 16

Jacka

daltervia

what did people get the radial velocity and why it wasn't close to c?

I got 10^-4.
I put that the reason was the density of the Sun.

Reply 17

hayyan

Jacka

I got 10^-4.
I put that the reason was the density of the Sun.

Same answer but i said that photons constantly colliding with nuclei (hydorgen and helium as fusion reaction goes on), cos i watched it in a documentary.

For the last question i got 1.12m for hight of fountaint. Also i got 1'234 Secs maybe something like that for the next question on kettle.
For the mass of galaxy thing, i got 10^41 kg.

The big mark questions were quite alright :smile:

Reply 18

royale_sufi

hayyan

Same answer but i said that photons constantly colliding with nuclei (hydorgen and helium as fusion reaction goes on), cos i watched it in a documentary.

For the last question i got 1.12m for hight of fountaint. Also i got 1'234 Secs maybe something like that for the next question on kettle.
For the mass of galaxy thing, i got 10^41 kg.

The big mark questions were quite alright :smile:

i remember getting something like 2000 secs for the kettle (like 34 minutes) , i dunno if im right or not, wat 2 reasons did you put for people not changing to using this form of power to heat their water?

i think i put that it takes too much time to heat (the obvious one) and that it may be expensive and people dont like change. Am i wrong?

Reply 19

ebam_uk

20

I said that the surface area required to heat the kettle, is too great, and therefore not practical to use, to heat a mass of water so little.

OCR A - Cosmology June 2008 How did it go ?

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