# X ray characteristic spectrum and bohr's relation

Discussion in 'Physics' started by logearav, Aug 17, 2012.

1. ### logearav Thread Starter Member

Aug 19, 2011
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Dear Revered Members,
Bohr's relation is ΔE = h$\upsilon$.
That is when an electron jumps from higher energy to lower energy a spectral line of frequency equal to energy difference between the higher and lower orbit is released.
That is $\upsilon$ = (E2 - E1)/h
Here I assume electron jumps from L shell to K shell, which are denoted by E2 and E1 respectively.
Now, while studying about X ray characteristic spectrum( please see my attachment) for K series line spectrum, electron jumps from L shell to K shell. But the frequency is given as Ek - El = h$\upsilon$. Shouldn't it be
El - Ek = h$\upsilon$?

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2. ### Kermit2 AAC Fanatic!

Feb 5, 2010
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In the text he refers to electrons in the innermost shells being more 'tightly' bound. From this point of view the algebra would be correct, but he gives no unit of energy or numbers.

The transistion from a higher energy shell to a lower energy shell does involve a loss of energy for that electron.(a photon is born) so from that viewpoint you are right and k-l should be l-k.

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3. ### studiot AAC Fanatic!

Nov 9, 2007
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It depends upon convention.

Physics mostly uses the convention that energy evolved or given off is negative.

So if your textbook is using this convention it is correct.

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4. ### Kermit2 AAC Fanatic!

Feb 5, 2010
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... that is pretty much what I tried to convey. It really is a matter of perspective.

The absolute value of the answer would be the same whether you do it with a negative answer or a positive one.

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