# I X-ray spectra- bremsstrahlung and characteristic x-rays

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1. Aug 15, 2016

Hi all,

In an x-ray spectrum, the curve part represents the bremsstrahlung part, and the spikes are the characteristics x-rays. Characteristic x-rays represent a discrete energy. However, in many textbooks, I noticed that the characteristic x-rays are often represented as a peak, which implies a range of energies.

Can anyone help me understand why this is so? Am I missing something?
Thanks!

2. Aug 15, 2016

### drvrm

In any experimental measurement a wave length or frequency is a number but the intensity plot will have a spread due to uncertainty in measurement and it comes out like a peak with a small spread.....this width say at half maximum is a measure of uncertainty ....as well as the state of emitter of that line ....if the source is in thermal motion the width increases .
Even in visible spectrum say Sodium doublet lines D1 and D2 you will find a width of emission lines.

Moreover if somebody tries to measure exactly the frequency i.e. the energy of the characteristic emission the Heisenberg Uncertainty relation will give an infinite width of the time span of measurement ....as uncertainty in energy and time multiplied together should be of the order of Planck's constant.

3. Aug 15, 2016