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/sci/ - Science & Math

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2385421 No.2385421 [Reply] [Original]

Given only a wavelength of an emitted photon, and the energy level of an electron that it has relaxed to (nfinal), how would one solve which energy level it initially fell from (for a hydrogen atom)?

Pic somewhat related.

>> No.2385429

I originally tried
hf = (Ef - Ei)
hf = (13.6/nfinal^2 - 13.6/ninitial^2)

with nfinal = 2, but somehow I kept solving for ninitial being 2 as well, which clearly would be wrong.

>> No.2385438

isnt it

Ef = Ei + hf

>> No.2385459

>>2385438
I'm solving for ninitial, not final
so I keep doing hf - Ef, and yet I keep getting the same n value.

>> No.2385488

L = wavelength
h = planck's constant
c = speed of light
nfinal = the orbit level it drops to = 2
ninitial = the level it came from = ?

So far I have done f = c/L
and then hf = Ef - Ei
which is hf = 13.6/nfinal^2 - 13.6/ninitial^2

hf calculates to 4.577e-21
and so I keep doing ((hf - (13.6/4))/ -13.6)
to be left with 1/ninitial^2
but ((hf - (13.6/4))/ -13.6) amounts to 1/4. 1/4 inverse is obvious 4, square-rooted being 2!
and it would make no sense that a photon could be released from the energy level not changing.

>> No.2385526

Bump
Anyone?

>> No.2385546

well, it fell, so it had to have come from the energy level above it.

duh.

>> No.2385574

>>2385546
Thanks for the sarcasm, you definitely helped answer the question o_o
No shit it has to have fallen from another energy level.

>> No.2385739

Look, i do remember doing something like this years ago at uni but i have been out for 5 years and so cant remember.

what i will tell you is your equation relating energy field to energy...the 13.6/n^2 uses big arse numbers relative to the value of hf u calculated.

ie

practically zero = 13.6/n2 - 13.6/m2

obiously n is practically gonna equal m

isnt there like 2 planc constants or something.

rule 1 in all science. make sure the units derived for are correct such that what ever random units the 13.6 or n has makes both sides of the equation dimensionally consistant