Andy Perrin Posted June 19, 2020 Share Posted June 19, 2020 Stefano please don’t use lambda for both attenuation length and wavelength in the same document. Also log base e should be ln(). Link to comment
bobfriedman Posted June 19, 2020 Share Posted June 19, 2020 perhaps use "Mu" for linear attenuation?? Link to comment
Stefano Posted June 19, 2020 Author Share Posted June 19, 2020 ex (in the second formula) is the entire base. Maybe my formulas can be simplified, if someone can tell me. Also in the third one the base is e with an exponent. Link to comment
Stefano Posted June 19, 2020 Author Share Posted June 19, 2020 The problem is that symbols are recycled in physics. In this case we have two lambdas, one for the wavelength and the other one for the attenuation length. Should I change the symbols? Link to comment
Stefano Posted June 19, 2020 Author Share Posted June 19, 2020 perhaps use "Mu" for linear attenuation??The lowercase version may generate confusion with "µm" (maybe not). Should I use another symbol not present in the document? Link to comment
Stefano Posted June 19, 2020 Author Share Posted June 19, 2020 Also, tell me if there are any broken links. Link to comment
bobfriedman Posted June 19, 2020 Share Posted June 19, 2020 The lowercase version may generate confusion with "µm" (maybe not). maybe not. Link to comment
Andy Perrin Posted June 19, 2020 Share Posted June 19, 2020 µ won't create any confusion with micrometers. The base of a logarithm shouldn't have any variables like x in it. If you do, you should be rewriting it differently, but in this case I think you have simply done it wrong. Remember, e is a number like π. e^x is a function. ln(x) = loge(x). My suggestions would be: Link to comment
dabateman Posted June 19, 2020 Share Posted June 19, 2020 The problem is that symbols are recycled in physics. In this case we have two lambdas, one for the wavelength and the other one for the attenuation length. Should I change the symbols? This reminds me of how to find a chem-physics person in a room. Ask what new (nu) and they or I will answer c/lambda. Link to comment
Stefano Posted June 20, 2020 Author Share Posted June 20, 2020 µ won't create any confusion with micrometers. The base of a logarithm shouldn't have any variables like x in it. If you do, you should be rewriting it differently, but in this case I think you have simply done it wrong. Remember, e is a number like π. e^x is a function. ln(x) = loge(x). My suggestions would be: Thanks Andy, they were so simple to obtain! I always do simple things in a too complicated way. I just had to do ln on both sides and than rearrange things. What I instead did was to separate the components of the exponent, and that led to my not-so-nice (but still working) formulas (I tested them). I don't know why sometimes I can't see a simple solution, even when I have it in front of my eyes. Link to comment
Stefano Posted June 20, 2020 Author Share Posted June 20, 2020 Tomorrow I will fix a few things... thank you all for the suggestions. Again, tell me if there is something else to fix, even minor things. Link to comment
StephanN Posted June 20, 2020 Share Posted June 20, 2020 Maybe I am thick, but "Also remember that a m-1 simply means a times in one meter. The length in meter is the reciprocal of a (1/a). If µ = 100 m-1, it means that µ = 0.01 m, or 1 cm." makes no sense. How can a length have the reciprocal of a length as a unit? I think I get what you're intending to say (in a colloquial way), but "m-1" in science is the reciprocal of a metre and used for the wavenumber (https://en.wikipedia.org/wiki/Wavenumber), for example. IMHO, you'd better not use "100 m-1" but rather "10-2 m". Link to comment
Andy Perrin Posted June 20, 2020 Share Posted June 20, 2020 StephanN, mu is meters here. Not 1/m. It is the attenuation length. Alpha is the absorption coefficient which is in 1/m units. Alpha = 1/mu. Link to comment
Stefano Posted June 20, 2020 Author Share Posted June 20, 2020 m-1 is not the length (although correlated), but something different. The length says how much units (meters, for example) are contained in a "length". The other thing says how much lengths are contained in a unit. (Yes, I know you know it). I wrote it to make things easier for people not used to this writing. It is another way to write a length, if you will. I had another idea: should I specify the differences between water vapor, liquid water and ice? Link to comment
Andy Perrin Posted June 20, 2020 Share Posted June 20, 2020 Stefano, you still have some problems up there. You are using µ for attenuation length (m) in some places but as absorption coefficient (typically called alpha) (m^-1) in other places. You can't use it for both. Is there any way you could let me edit this? If µ = 100 m-1, it means that µ = 0.01 m, or 1 cm.That's an example where you used two units for the same quantity in one sentence. Correct this (and all similar errors) to: If a = 100 m-1, it means that µ = 0.01 m, or 1 cm. Or you can send it to me and I'll fix it for you if that's easier. Link to comment
Stefano Posted June 20, 2020 Author Share Posted June 20, 2020 It is the same for me (I can edit myself). If you will modify it, do you mean to send you the text, and then you will send me back the edited version? Or, can Andrea give you the ability to modify it? I fear links will break if I copy-paste them. Link to comment
Stefano Posted June 20, 2020 Author Share Posted June 20, 2020 Maybe it will be simpler if I modify them. Should I use the greek letter α? Link to comment
Andy Perrin Posted June 21, 2020 Share Posted June 21, 2020 Yeah use the Greek. As long as you are clear feel free to edit yourself. Otherwise I meant to send me the text. Link to comment
Stefano Posted June 21, 2020 Author Share Posted June 21, 2020 Keep in mind that I don't have a source for my text, I am writing it directly here. So what you see posted is the actual text. Link to comment
Andy Perrin Posted June 21, 2020 Share Posted June 21, 2020 No, I mean the text with the formatting symbols intact (square brackets, etc.) Link to comment
StephanN Posted June 21, 2020 Share Posted June 21, 2020 Sorry about my wrong way of putting it. Actually, what I couldn't get over was exactly the thing that Andy mentioned: You can't have two different units for the same quantity in an equation, and using the same letter for two different quantities (in the same context! Of course, in physics and mathematics, symbols must be reused, but never in the same set of equations) is also a foolproof way into all sorts of misunderstandings Link to comment
Stefano Posted June 21, 2020 Author Share Posted June 21, 2020 Today (later) I will fix a few things... my post gets better every time. It must be correct, written the right way. Link to comment
Stefano Posted June 21, 2020 Author Share Posted June 21, 2020 Did I insist too much on the difference between "µ" and "α"?Also (again) should I talk (briefly) about the differences between the three states of matter (of water), that is water vapour, liquid water and ice? Link to comment
Stefano Posted June 21, 2020 Author Share Posted June 21, 2020 Ops, seems like I wrote “µ” in italic... will fix that... ...just noticed that the style of this symbol depends on the device (maybe the OS) on which you see it. It isn't written in italic. Link to comment
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