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This is first of questions, I may have more, hence the very general title of the thread. I know the basic optics involved, two most important things here are Snell's law and the concept of critical angle - no problems here, even if I am just skimming on the surface.
Problems start when I am trying to find how the refractometers are built and work. While there is plenty of information available, it is often either contradicting itself or unclear. For example - I am trying to find how Pulfriсh refr. is made. Some sources claim it is a critical angle device (see for example here, definition is taken from McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.), and show this (or equivalent) picture:
(this particular one is from wikipedia). OK, θ is a critical angle, we measure φ as it appears as the bright-dark boundary, some simple math and we have n of sample.
But other sources - like this http://www.uni-leipzig.de/~prakphys/aprak/english/optics/O-05e-AUF.pdf and Optical sensors and microsystems: new concepts, materials, technologies book - show pictures similar to this one:
While it is obvious how it works, it is very different and it is not a critical angle device.
So, which one it is?
Problems start when I am trying to find how the refractometers are built and work. While there is plenty of information available, it is often either contradicting itself or unclear. For example - I am trying to find how Pulfriсh refr. is made. Some sources claim it is a critical angle device (see for example here, definition is taken from McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.), and show this (or equivalent) picture:
(this particular one is from wikipedia). OK, θ is a critical angle, we measure φ as it appears as the bright-dark boundary, some simple math and we have n of sample.
But other sources - like this http://www.uni-leipzig.de/~prakphys/aprak/english/optics/O-05e-AUF.pdf and Optical sensors and microsystems: new concepts, materials, technologies book - show pictures similar to this one:
While it is obvious how it works, it is very different and it is not a critical angle device.
So, which one it is?