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Topic: More physics than chimestry  (Read 862 times)

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Offline Chimystlearner

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More physics than chimestry
« on: January 03, 2019, 03:02:08 PM »
Hi, I know that it not a forum of physicis, but anyways I would like to try to ask you whats happening in the following.
First of all there is a source of radiation, specifically "Radio" which emits a fixed steady energy. But I have put on its way several laminas of poliethilene. 1 piece of 0,2cm, 2 pieces(0,4), 3 pieces(0,6cm) Ive got different values( something normal) in the lab. But I do not know why at the moment of calculating the linear attenuation coefficient is different in each case. Should it not be the same in those three?  In fact it is the same material, the only thing is different, it is the distanced travelled. So I do not know the reason of these different results.
This question is just because the exercise asks me about the linear attenuation coefficient of the material. But I have come across with this problem... Thanks

Offline mjc123

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Re: More physics than chimestry
« Reply #1 on: January 04, 2019, 04:54:36 AM »
Why not show us the data you have obtained, and how you calculated the attenuation coefficient. Otherwise it's very hard for us to see what the problem might be.

Offline Enthalpy

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Re: More physics than chimestry
« Reply #2 on: January 04, 2019, 07:39:22 AM »
Don't forget to tell us the wavelength or frequency of your experiment.

If the wavelength is similar to the obstacles' dimensions, as is very often so with radio waves, these don't propagate like light does through macroscopic items. Diffraction gets the most important behaviour.

Plain polyethylene has nearly no losses for radio waves, normally too low to measure, except at THz frequencies. The main effect is reflection at the interfaces resulting from the permittivity step (neither a big effect). Resonances by the material thickness and by the distances between the sheets would bring an attenuation very different from what losses do.

You could try to measure the attenuation by each sheet separately.

Offline mjc123

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Re: More physics than chimestry
« Reply #3 on: January 04, 2019, 07:51:19 AM »
If you're looking for a physics forum, try here:
https://www.physicsforums.com/

Offline Enthalpy

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Re: More physics than chimestry
« Reply #4 on: January 04, 2019, 04:22:34 PM »
But I'm here and not at Physicsforums.  ;D

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