# Need help! quantum physics

#### stickplot

1. The problem statement, all variables and given/known data

ok so i know whenever a photon is absorbed it will jump up a energy level and when it is emmited it releases energy. but my question is, for example, if k=1 (fundamental state) in a hydrogen atom and they give you the given wavelength of the photon, you solve it and you get n=2 would the photons absorb or emit? im just confused because at first i thought it would absorb, because it is a greater number but then i used the equation -13.6/n^2 and got me confused because k= -13.6 and n= -3.4 and i thought that the electron with the greater negative number is "stronger" because it attracts more, and i thought that for a photon to absorb it had to have "at least" as much energy as the electron it hits. So would it emit or absorb? do i have the wrong idea of whats going on? someone help please and explain to me.
thank you :)

2. Relevant equations
1/lambda= r(1/k^2-1/n^2)
hf= hc/lambda= energy of transition= energy of photon

#### Hootenanny

Staff Emeritus
Gold Member
ok so i know whenever a photon is absorbed it will jump up a energy level and when it is emmited it releases energy. but my question is, for example, if k=1 (fundamental state) in a hydrogen atom and they give you the given wavelength of the photon, you solve it and you get n=2 would the photons absorb or emit? im just confused because at first i thought it would absorb, because it is a greater number but then i used the equation -13.6/n^2 and got me confused because k= -13.6 and n= -3.4 and i thought that the electron with the greater negative number is "stronger" because it attracts more, and i thought that for a photon to absorb it had to have "at least" as much energy as the electron it hits. So would it emit or absorb? do i have the wrong idea of whats going on? someone help please and explain to me.
thank you :)
It seems that you are quite confused about Hydrogen transitions. For a brief overview take a look http://hyperphysics.phy-astr.gsu.edu/hbase/hyde.html" [Broken].

It is extremely difficult to actually 'teach' concepts through a forum, perhaps if you posted the specific question that you are having trouble with we could help you out.

Let's have a look at what you have said:
ok so i know whenever a photon is absorbed it will jump up a energy level and when it is emmited it releases energy
Let me just add a few words:
Whenever a photon of the correct* energy is absorbed by an electron, the electron will jump up a energy level and when a photon is emmited the electron looses energy.

*By correct energy, I mean an energy corresponding to the difference in energy between the electrons current energy level and another (higher) allowed energy level.

if k=1 (fundamental state) in a hydrogen atom and they give you the given wavelength of the photon, you solve it and you get n=2 would the photons absorb or emit?
Well, the electron is moving from the energy level n=1 to n=2, i.e. it is moving from a lower energy level to a higher one.

but then i used the equation -13.6/n^2 and got me confused because k= -13.6 and n= -3.4 and i thought that the electron with the greater negative number is "stronger" because it attracts more, and i thought that for a photon to absorb it had to have "at least" as much energy as the electron it hits.
I honestly have no idea what you are talking about here or where you have pulled n=-3.4 from. By definition n can only take integer values. You also seem to be using the same symbols for two different meanings and vice versa. In the previous quote you seem to be using both k & n to denote energy levels, whereas here you seem to be using them to denote energies.

As I said above, it is probably best if you post the question that you are struggling with an we can help you through it. I know that from our previous conversations that you are following an online course, what are you using for course materials/texts?

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#### stickplot

ok appreciate your help. heres the question
A photon with λ = 600 nm interacts with a hydrogen atom in fundamental state. Will the photon be absorbed? Justify your answer.
and btw im homeschooled and im taking the ut austin high school program, and we dont get text books but its an online course so it gives you a video for the tutorial, but there are some tutorials that i get quite confused with.
and the -13.6/n^2= energy of orbital. and i thought you were supposed to use what you found for n to place in the equation to find the energy.
if you guide me through the question it will certainly help thank you :)

#### Hootenanny

Staff Emeritus
Gold Member
ok appreciate your help. heres the question
A photon with λ = 600 nm interacts with a hydrogen atom in fundamental state. Will the photon be absorbed? Justify your answer.
and btw im homeschooled and im taking the ut austin high school program, and we dont get text books but its an online course so it gives you a video for the tutorial, but there are some tutorials that i get quite confused with.
and the -13.6/n^2= energy of orbital. and i thought you were supposed to use what you found for n to place in the equation to find the energy.
if you guide me through the question it will certainly help thank you :)
Okay so we have the equation, but is is equally important to know the units that we are working in. So, what are the units of the quoted -13.6?

#### stickplot

electron volts.
so we find n first right

#### Hootenanny

Staff Emeritus
Gold Member
electron volts.
so we find n first right
How do you propose to find n if we don't yet know the energy of the incident photon?

#### stickplot

o ok. well the energy of the photon would be hc/lambda which would be 2.1 eV nm but why do we need this?
i thought that you could just find n by putting in lambda and k (fundamental state) on the 1/lambda=1/k^2-1/n^2 and solving for n

#### Hootenanny

Staff Emeritus
Gold Member
o ok. well the energy of the photon would be hc/lambda which would be 2.1 eV nm but why do we need this?
i thought that you could just find n by putting in lambda and k (fundamental state) on the 1/lambda=1/k^2-1/n^2 and solving for n
You could indeed use that equation (but don't forget the coefficient).

Since you mentioned the other formula in your previous post, I assumed that you wanted to use the alternative formula:
and the -13.6/n^2= energy of orbital. and i thought you were supposed to use what you found for n to place in the equation to find the energy.

#### stickplot

alright.
so i solved for n and i got 1.08 and since only integers are accepted i would round off to 1 right?
and since k=1 and n=1 how do i know whether it is absorbing or not?

and how could i solve with the other equation? once i found the energy of the photon what would i do after?

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