G485 June 2012 Paper and unofficial mark scheme

The specification.

The original wavelength would be the one that wasn't redshifted, so the 480.

Reply 23

zabuzar

god, you just gave me a heart attack
wow
look at the question paper again, its in the first post, the 480.0nm is the spectrum from distant galaxy
it threw me off too that the redshifted one is so rounded and 'perfect' and the original isn't.

Reply 24

But the one as viewed from Earth WILL be redshifted, so you want to use the 480.

Reply 25

Pachydermal

if you look at the wording it says "spectrum of calcium as observed from a source on earth and from a distant galaxy" so the 393.4 one is the non redshifted one

Reply 26

bdfzyt

6

can we get 1 mark if used 480.....?

Reply 27

zabuzar

thank you
at least i used the correct values

Reply 28

You have to use the 393.4 nm wavelength on the bottom of the equation d(lamda)/lamda = v/c.

For the galaxy question:

F = GMm/r^2
= (6.67x10^-11 . 10^41 x 10^41)/(4x10^22)^2

Reply 29

The source as observed from Earth was 393.4nm, the one from the galaxy was 480nm, you use the one from the galaxy, because it hasn't been redshifted.

Reply 30

bdfzyt

6

Original post by joefoxon

The source as observed from Earth was 393.4nm, the one from the galaxy was 480nm, you use the one from the galaxy, because it hasn't been redshifted.

I also used 480. But it looks that we were wrong...
I just wonder can we get at least 1 mark for that question..,

Reply 31

Original post by joefoxon

The source as observed from Earth was 393.4nm, the one from the galaxy was 480nm, you use the one from the galaxy, because it hasn't been redshifted.

Umm ... 480 nm is the wavelength observed from a distant galaxy, so I think that would be the one that was red-shifted.

Reply 32

But we are observing the galaxy, not the Earth. And if you look at the galaxy from the galaxy. it won't be redshifted.

Reply 33

Hey joefoxon,
Do you mind showing me your full working. I think I may be misunderstanding you.
Cheers

Reply 34

bdfzyt

6

In my opinion, the grade boundary is: A* 76, A 69, B62, C55...
Anyone agree with me?

Reply 35

Pachydermal

Original post by joefoxon

But we are observing the galaxy, not the Earth. And if you look at the galaxy from the galaxy. it won't be redshifted.

As i said a minute ago the wording was "the spectrum of calcium as observed from a source on the earth and from a distant galaxy" so you want to use the earth one as non redshifted

Reply 36

Original post by Pachydermal

As i said a minute ago the wording was "the spectrum of calcium as observed from a source on the earth and from a distant galaxy" so you want to use the earth one as non redshifted

Yep I agree ... thanks!

Reply 37

Jamiethevamp

Original post by zabuzar

i got 1320Mpc
there was a decimal point and a digit after but i rounded to 3s.f.

I used the value i got in my calculator and got 1320.79 then rounded to 1321? but when i wrote down the value i got i wrote 6.60x10⁷, reckon i have still got the mark? :confused:

Reply 38