balmer series question (1 Viewer)

[sikeveo]

this question is majorly pissing me off

http://img484.imageshack.us/img484/5948/question30sg.gif

 

[serge]

sounds like the old syllabus to me...
I dont think new books contain Bohrs orbits info

the 2001 excel i have has some sort of stuff like that
but i just ignored it and turned the page...

anyone know if we actually need it?

 

[KFunk]

That's a pretty stupid question 'cause it's just testing algebra. With a bit of manipulation I suspect that the answer is A.

EDIT: A way you could reason it is that both C and D have the (n² - 4) or (4 - n²) bit on top, which they shouldn't, making them incorrect. B only has h² whereas it should really have enough h terms to make up h³ hence B is also incorrect. Probably quicker to do that than go through the algebra.

 

[serge]

That's a pretty stupid question 'cause it's just testing algebra. With a bit of manipulation I suspect that the answer is A.

wait, but what dotpoint says we have to know it?

 

[sikeveo]

Suspicions lead to incorrect answers Kfunk. A is not correct.

 

[Captain Gh3y]

It was removed 3 years ago

 

[serge]

It was removed 3 years ago

Praise the Lord!
hallelujah!

 

[KFunk]

Suspicions lead to incorrect answers Kfunk. A is not correct.

Strange, because I can't see how the others would be correct.

 

[sikeveo]

Yeh i dont care whether its in the syllabus or not, i want to find out how to get to the answer.

 

[KFunk]

Do you know which one is the correct answer?

 

[sikeveo]

Strange, because I can't see how the others would be correct.

Well i cant see how any are correct, but C is.

 

[acmilan]

The answer is A. Basically you just replace v₂ with c/lambda, then solve for lambda.

edit: i just read the above, i don't see how any other ones can be right :S

 

[KFunk]

Well i cant see how any are correct, but C is.

Hmm, I'm pretty sure it's A not C but then again my basic algebra/arithmetic ain't that hot.

 

[sikeveo]

The answer is A. Basically you just replace v₂ with 1/lambda, then solve for lambda.

edit: i just read the above, i don't see how any other ones can be right :S

You said C!!!!!!!!! Damn you vince.

 

[acmilan]

You said A!!!!!!!!! Damn you vince.

Haha i never said it was C

that was groves:

[17:33:54] <groves> it's C
[17:34:20] <_droid|> how'd u get it so fast?
[17:34:32] <groves> i'm good

 

[serge]

Yeh i dont care whether its in the syllabus or not

its that kind of attitude that'll push all the syllabus knowledge out
(will it would for me anyway)

 

[KFunk]

Well i cant see how any are correct, but C is.

letting y = lambda = wavelength

v = c/y = - (m/4.pi.h)(e²/4.pi.E.h)²[(4 - n²)/4n²)

c = y . (m/4.pi.h³)(e²/4.pi.E)²[(n² - 4)/4n²)

y = [16.pi.h³n²c]/[m.{e²/4.pi.E}²(n² - 4)] = A

 

[The MJB]

If you look closely, you'll see that A = 1 / C