Refractometry Flashcards
What is Polychromatic Light?
Light that consists of more than one wavelength.
What is Refractometry?
Refractometry refers to the measure of the Index of Refraction.
What is the most common method of measuring Refractive Index?
Immersion Method: where an unknown, transparent grain mount RI is compared to an immersion oil RI.
What is Relief?
Relief is the degree to which the mineral grain stands out from the immersion oil.
If RI of medium & oil are NOT the same, the grain stands out because light is REFRACTED.
Relief of _______ minerals may change as the stage is rotated in plane light.
Anisotropic
Positive Relief –> If the RI of mineral is ____ than oil.
Negative Relief –> If the RI of mineral is ____ than oil.
Positive Relief –> RI is higher in mineral.
Negative Relief –> RI is lower in mineral.
How do you find the Becke Line on a mineral grain?
It is the light band/rim around the mineral
How is the Becke Line formed?
The Becke Line is created from the convergence of light to the normal as it is refracted through the mineral grain of a HIGHER Refractive index.
Explain the difference between a converging lens and a diverging lens in a mineral grain?
A converging lens will occur if light is passed through a mineral of higher RI and will refract (converge) toward the normal.
A diverging lens will occur if the RI in the mineral grain is less than the surrounding oil, and will diverge toward the higher RI.
What is the difference between reflection and refraction?
Reflection is when light bounces off a surface.
Refraction is the bending of light as it travels from one medium to another.
High Refractive Index –> ___ Velocity
Low Refractive Index –> ____ Velocity
High Refractive Index –> Low Velocity.
Low Refractive Index –> High Velocity.
Light is refracted toward the ______ when passing through a mineral of _____ RI.
Medium/Higher
If light isn’t refracted through the grain at all, it has ___ relief.
No relief.
If the white line (Becke Line) is on the inside border of the grain, the RI is ___. If the white line is on the outside, the RI is ___.
High/low.
