# Photoelectric EffectWatch

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#1
The diagram shows some of the electron energy levels for the hydrogen atom with four possible transitions.

The transition that would result in the emission of the longest wavelength is:
A - -13.6eV to 0eV
B - 0eV to -13.6eV
C - -0.85eV to 0eV
D - 0eV to -0.85eV

The answer is D and I'm trying to understand why... So we have . If E is small then f must be small also, and because , the only way can decrease is if increases.
I think I've just answered my own question.

Secondly, if something goes from ground state to a negative energy level e.g. decreasing energy level, does that mean it's emitting a photon of Energy ?
0
6 years ago
#2
As far as I know an atom cannot go from its ground state to a lesser energy level; the ground state is the most stable state where all its elections are in the least possible energy level.

I reckon the more negative the energy level the more energy it has absorbed and more excitation.

It has to be C. To emit a photon it should go from a higher energy level to a lower one (more negative to less negative) and to absorb it should be vice versa. So if it results in emission of the longest wavelength (smallest frequency) the change has to be the least. So it is C.

Where's the diagram? Did you read the answer from the marking scheme properly?

Sent from my GT-I9001 using Tapatalk
0
6 years ago
#3
(Original post by lmsavk)
The diagram shows some of the electron energy levels for the hydrogen atom with four possible transitions.

The transition that would result in the emission of the longest wavelength is:
A - -13.6eV to ground state
B - ground state to -13.6eV
C - -0.85eV to ground state
D - ground state to -0.85eV

The answer is D and I'm trying to understand why... So we have . If E is small then f must be small also, and because , the only way can decrease is if increases.
I think I've just answered my own question.

Secondly, if something goes from ground state to a negative energy level e.g. decreasing energy level, does that mean it's emitting a photon of Energy ?
Could you please post the actual diagram and question. What you have written there doesn't make sense.
-13.6eV is the ground state of hydrogen, so how can you have a transition "ground state to -13.6eV"?
0
#4
(Original post by Stonebridge)
Could you please post the actual diagram and question. What you have written there doesn't make sense.
-13.6eV is the ground state of hydrogen, so how can you have a transition "ground state to -13.6eV"?
I was taking ground state to be 0eV
0
6 years ago
#5
(Original post by lmsavk)
I was taking ground state to be 0eV
Well this is where you are misunderstanding.
The ground state is the lowest energy level. Here it's -13.6 eV.
So you haven't written the question out correctly. That's why we ask on this site that you always post the actual and complete question, and not your interpretation or paraphrase of it. That way you will get the help you need.
0
6 years ago
#6
To emit a photon the electron must fall to a lower level.
That leaves just B or D as possible correct answers.
The longest wavelength corresponds to the smallest energy loss.
0
#7
(Original post by Stonebridge)
Well this is where you are misunderstanding.
The ground state is the lowest energy level. Here it's -13.6 eV.
So you haven't written the question out correctly. That's why we ask on this site that you always post the actual and complete question, and not your interpretation or paraphrase of it. That way you will get the help you need.
Sorry . So, with that in mind, does the question make sense now?
0
#8
(Original post by Stonebridge)
To emit a photon the electron must fall to a lower level.
That leaves just B or D as possible correct answers.
The longest wavelength corresponds to the smallest energy loss.
Because and if h is tiny then because , rearranging, , so when f is small is large?
Also if something decreases in energy level, does that mean it's emitting a photon of energy ?
And if something increases in energy level, does that mean it's absorbing a photon of energy ?
0
6 years ago
#9
(Original post by lmsavk)
Because and if h is tiny then because , rearranging, , so when f is small is large?
Also if something decreases in energy level, does that mean it's emitting a photon of energy ?
And if something increases in energy level, does that mean it's absorbing a photon of energy ?
Yes. Absorbing a photon causes the electron to gain energy so it moves up to a higher level. Losing energy means the electron emits a photon.

Yes
E=hf = hc/λ

So greater energy means greater frequency, which means shorter wavelength.
Less energy means lower frequency, which means longer wavelength.
0
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