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18 Mar 2009 00:21:03 IST
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Let us consider a sample of hydrogen atoms and in each atom, the electron is excited to the energy level n. What is the maximum number of unique wavelengths this sample can emit?



I don't have the answer with me. So, please give the explanation part also, not just the answer.


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revenge's Avatar

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18 Mar 2009 01:14:21 IST
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n(n-1)/2  .  [not sure]

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18 Mar 2009 01:19:31 IST
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I think what you seems to have done is nC2.

 

Since I don't have the answer to this question, I cannot say whether it's correct or not. But according to me, the answer given by you is not correct since the question is asking for unique wavelengths in the sample.

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18 Mar 2009 01:21:06 IST
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ok  got  it,  i have  done  many repetitions.

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18 Mar 2009 10:47:21 IST
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see the following case assuming n = 4

 

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18 Mar 2009 10:50:29 IST
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here, you can see that total no. of wavelengths possible is 4 (4-1)/2 = 6. hence the formula is correct. I cannot xplain but I think you can see from the figure that as n increases, no. of wavelengths increases by n-1 because e has now n-1 more choices to dexcite

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18 Mar 2009 11:06:37 IST
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Well, I think what you are saying is correct.

 

But one thing is sure that we cannot come from n to n-1 to n-2 to .........1. Because that case will have repetitions. What do you have to say???

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18 Mar 2009 11:27:06 IST
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But all the electrons have been excited to nth energy state. Then how did in the rest of the transitions, except for the first one, the transitions have not started from nth enery level. Can you please explain???

 

Well, I rated you and accepted your answer but didn't realize about the present doubt. Anyways, can you please answer???

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18 Mar 2009 11:32:43 IST
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basically..

the correctest (a nu word )...xplaination is this

..

had it been a single hydrogen atom ...the no. of unique lines wud be .??? !!! ONLY ONE ..

but as there are many atoms of hydrogen ...so there are repetitions ...

but as a viewer ..one wud see ..nc2 types of lines ..(.all unique ) ..

these lines wud be comin from different atoms...

but make it clear ..that a single atom wud be giving a single line however.

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18 Mar 2009 11:34:52 IST
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I have included all the cases. I mean, I have included n=3 to n=2, n=2 to n=1, n=3 to n=1etc.
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18 Mar 2009 11:40:29 IST
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But don't you think that you have also considered the repetitions.

See, suppose there are n Hydrogen atoms. In each one of them, the electron has been excited to the nth energy level. Now to come to the ground state, it can make various types of transitions. Lets say first it comes from n to n-1, then to some other energy level. But Besides this electron, there are n-1 other electrons that are also making transitions. So, don't you think that the transitions described by you will repeat.

 

Please answer.

 

 

@Nugorama

For a single H-atom, there are n-1 unique wavelengths, not ONLY ONE.

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18 Mar 2009 11:44:09 IST
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@ASHISH KUMAR..try to understand..when one single atom excites...it has n-1 choices to de-excite...but it choses ONLY ONE ..from these n-1...had the question been for a single atom ..answer wud be surely ONE..please ..we r going to need xperts here..
XYZ's Avatar

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18 Mar 2009 11:52:23 IST
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The question asks us to find the maximum number of unique wavelengths that this sample can emit.

 

And regarding this, for a single H-atom, the transitions have to be from n to n-1 to n-2 to n-3 to ...........n=1. So, in all, we have n-1 unique wavelengths.

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18 Mar 2009 11:55:53 IST
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i ask u ...

in how many ways can u press a key of ur keyboard..??

u say 105 or 106 ...

then u press a key..

now i ask u ..how many different keys u just pressed..??

u still say 105 or 106..

did u pressed all the keys ..or JUST ONE??

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18 Mar 2009 12:05:38 IST
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You are confused between the number of transitions.

Here the question does not say that the number of transitions have to be one. It is not necessary that it has to reach the ground state in just one jump. But it just asks that what are the maximum number of unique wavelengths it can emit???

 

 

There was a question before the question that I have given here which asked us to find the no. of unique wavelengths for one H-atom. And its answer was n-1. The solution is also given.

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18 Mar 2009 12:08:34 IST
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FORGET THE above question ..and answer this ..that when a single atom of hydrogen is xcited to nth level..how many diff wavelengths we wud see ??
NugoRama's Avatar

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18 Mar 2009 12:08:58 IST
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be quick.
XYZ's Avatar

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18 Mar 2009 12:10:45 IST
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See, if we are free to make any number of transitions, we would see n-1 unique wavelengths.

 

But if we are allowed to make only one transition, then obvoiusly one.

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18 Mar 2009 12:14:12 IST
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wait

bhumi garg's Avatar

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18 Mar 2009 12:33:06 IST
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hey cud u ppl help me out wit light intensity n photon intensity? they r basically same o they have sum diffrence??????????? plz if u if any of u r moyed wit the ans then plz..........................




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