# Option: Astrophysics (1 Viewer)

#### Master Sword

##### New Member
ravdawg said:
If you understand where the distance modulus formula came from the q comes out:

M = m - 5log (d/10), as d is in parsecs and you know M is magnitude 10 pc away the formula in other words is:

m1 = m2 - 5log (d2/d1), sub in values and you get the answer. THe thing thoguh with this qustion was that if you didn't know d was in parsecs you wouldve got the right answer...

Kinda screwed over the people knew that, and helped the people who didn't!
Haha, yeah I used the M = m - 5log(d/10) formula first and substituted 1 for d from Earth to the Sun and 10 for d from Saturn to the Sun. Ended up finding the apparent magnitude but crossed it out thinking I'd done it wrong. Spent another page working out what 1 AU was in parsecs then substituted it all in and got the same answer...

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#### rayd

##### New Member
the correct answer to the saturn question is -21.5 .
the way you were meant to do it was by using the table in question d)
they gave both the aparent and absolute. then use the distance modulus to find what 1AU was in parsecs. then times that by 10 to find what 10AU was in parsecs then use the distance modulus again to find the apparent magnetude.

#### snrboffin

##### New Member
What was the Saturn question? On the H-R diagram I couldn't decide whether Arcturus was MS or red giant and wrote red giant only to scribble it out and put MS. When I got home I found out it was red giant. Hrrrmph. It was a little too borderline on the HR diagram for my liking and other people in my class had the same difficulty.

#### barling89

##### McLovin it :D
thanks tim! :wave:

#### Master Sword

##### New Member
asparagushills2 said:
yeah same here except i endeed up with something like -23, which is WAY too bright, but marks for working out!
Doesn't seem too farfetched to me. If you consider that Saturn is in the same solar system and the result you got is a bit dimmer than the apparent magnitude from Earth, it seems alright. Remember the distance from Saturn to the Sun is nowhere near the distance to the nearest star. I think I got somewhere between -21 and -23 also (can't remember).

#### barling89

##### McLovin it :D
does anyone know whether or not they scale the option topics? It might sound stupid but theres gotta be a difference in difficulty

#### Master Sword

##### New Member
barling89 said:
does anyone know whether or not they scale the option topics? It might sound stupid but theres gotta be a difference in difficulty
HANDY ANDY!

If you're asking whether certain option topics are scaled better then others then no apparently that's not the case. The candidates of each option topic will be ranked within each option topic and the top candidate in each option topic will be given the same mark. Second top candidate will get the 2nd best same mark, etc so the candidates in each option topic with each corresponding rank will be given the same mark for their rank, in turn making all option topics equal. That's what I've been told anyway.

But I'm pretty sure Physics as a whole is scaled up slightly. Not by a huge amount but you'll probably gain a few marks in the end.

~ 2t ~

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#### J Biddy

##### New Member
barling89 said:
does anyone know whether or not they scale the option topics? It might sound stupid but theres gotta be a difference in difficulty
I thought each option was designed so that when it's done each is as hard as any other. I know at school we had Quanta and Astro and one age of silicon, and the top guys in Quanta got 2 more that the top guys in astro but it didn't scale at all.

The H-R diagram was very difficult given the circumstances so hopefully the markers will be lenient.

#### ballin

##### Banned
ok these were my answers... discuss:

a) i) just talked about the 4 methods of detection for 4 different binary type stars - should be 2/2

ii) using M= m - 5log d/10, i got -21.5 which seems to be right, so 3/3

b) i) talked about using spectroscope to examine reflected sunlight which is of course light from a star and how it helped to deduce chemical composition 2/2

ii) talked about rotational v and density 4/4

c) talked about advances in space exploration tech. eg, GAIA and HIPPARCOS as well as photoelectric technologies - 5/7

d) i) using distance modules m - M, if m - M is greater than 0 then star is furthest away... so in this case its Betelgeuse 1/1

ii) LOL. i suck. worst diagram ever. 1/3

iii) no time 0/3

so yeah, 19/25 hopefully