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level: Tools in Depth - The refractometer

Questions and Answers List

level questions: Tools in Depth - The refractometer

Question	Answer
What can be placed on the eyepiece of a refractometer to help determine if the material is isotropic or anisptropic with birefringence?	Polarizing filter
When rotating a stone during testing on the refractometer, what needs to be maintained in order to get an accurate reading?	Position
If there is one shadow edge visible as pictured, what sort of material is being tested on the refractometer?	Isotropic
If there are two, unmoving shadow edges visible as pictured, what sort of material is being tested on the refractometer?	Anisotropic, Uniaxial
If there are two shadow edges visible as pictured, one constant and one moving that touch, what sort of material is being tested on the refractometer?	Anisotropic, uniaxial
If there are two shadow edges visible as pictured, one constant and one moving, but not touching, what sort of material is being tested on the refractometer?	Anisotropic, uniaxial or biaxial
If there are two shadow edges visible as pictured, one constant and one moving that intersect, what sort of material is being tested on the refractometer?	Anisotropic, biaxial
If there are two, moving shadow edges visible as pictured that do not touch, what sort of material is being tested on the refractometer?	Anisotropic, biaxial
If there are two, moving shadow edges visible as pictured that touch, what sort of material is being tested on the refractometer?	Anisotropic, biaxial
What is the name of the technique used if obtaining a reading from a stone is difficult as it is curved, or the facets are too small, to get an approximate reading?	Distant Vision
What distance should you keep your eye from the eye piece on the refractometer when using the distance vision technique?	30-60 centimeters
What will be seen through the eyepiece on the refractometer when using the distant vision technique, caused by the liquid droplet connecting the stone with the glass table?	Round/oval shape
If the round/oval droplet appears dark when using the distant vision technique, what does this mean?	RI of stone is higher
If the round/oval droplet appears light when using the distant vision technique, what does this mean?	RI of stone is lower
If the round/oval droplet appears half light and dark, with a line across the middle when using the distant vision technique, what does this mean?	RI of stone is at centre of droplet
True or False - The distant vision technique is less accurate than the standard method of RI testing	True
What is the name of the technique used to test tiny or otherwise difficult stones that would otherwise be untestable by using a white/monochromatic light to directly illuminate the stone?	Bright Line
When using the bright line technique, what do you look for through the eyepiece to get your reading?	Rainbow line
What is the name of the instrument that uses the reflection from a stones surface to give an RI reading?	Reflectivity Meter
What is it important to ensure when testing a stone using a reflectivity meter, due to using surface reflection?	Stone is clean
What is the term used to observe the effects of dispersion, DR and RI using a small, bright light source alongside another instrument such as the x10 loupe?	Visual optics