Optical Minerology Study Guide

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64 Terms

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Wave Speed Equation

Frequency is fixed

<p>Frequency is fixed</p>
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Velocity

c

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Frequency

f

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Wavelength

λ

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Refractive Index

n is always positive

<p>n is always positive</p>
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Retardation and Birefringence

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Vector Resolution

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Retardation

Δ

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Thickness

d

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Birefringence

δ

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Electric and Magnetic Vectors

Vibrate perpendicular to each other and perpendicular to the ray

<p>Vibrate perpendicular to each other and perpendicular to the ray</p>
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Visible Light

400-700 nm

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Particle Theory

Stream of photons

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Factors that Affect Electric and Magnetic Vectors

Refraction, Polarization, and Interference

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Wave Front

Surfaces connecting equivalent points on adjacent waves (dark planes)

<p>Surfaces connecting equivalent points on adjacent waves (dark planes)</p>
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Wave Normal

Lines perpendicular to wave front

<p>Lines perpendicular to wave front</p>
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Isotropic Wave Front

Wave normal and light rays are perpendicular to the wave front

<p>Wave normal and light rays are perpendicular to the wave front</p>
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Anisotropic Wave Front

Light rays are typically not parallel to the wave normal

<p>Light rays are typically not parallel to the wave normal</p>
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Wave Interference

Where waves vibrate in the same plane

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In Phase Wave Interference

Perfectly constructive, A+B=R

<p>Perfectly constructive, A+B=R</p>
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Out of Phase Wave Interference

Perfectly destructive, A+B=R

<p>Perfectly destructive, A+B=R</p>
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Double Refraction

Mineral forces light to vibrate in only 2 orientations that are mutually perpendicular

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Refraction

Light slows down and is bent toward the normal when it passes through two materials

<p>Light slows down and is bent toward the normal when it passes through two materials</p>
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Polarization

Restricting vibration directions of light waves so that they vibrate in a specific, orderly plane rather than randomly in all directions

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Unpolarized Light

The light vibrates in all directions perpendicular to propagation direction

<p>The light vibrates in all directions perpendicular to propagation direction</p>
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Plane Polarized Light

The electric vector vibrates in a single plane

<p>The electric vector vibrates in a single plane</p>
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Vibration Direction

Specific geometric orientation along which the electric vector of light wave vibrates as it travels through a medium

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Indicatrix

Sphere or ellipsoid created by plotting the refractive indices of a mineral as radii parallel to the vibration directions of light

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2 Things that the Indicatrix Tracks

Vibration Direction and Refraction Index

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What is seen when we look down the X plane?

Y and Z planes

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What is seen when we look down Z plane?

X and Y planes

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Preferred Vibration Direction of Upper Polar

Perpendicular to Lower Polar

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Isotropic Indicatrix Shape

Sphere

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Anisotropic Indicatrix Shape

Ellipsoid (Frisbee or Football)

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Isotropic Behavior Under Crossed Polars

Stays completely dark as stage rotates

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Anisotropic Behavior Under Crossed Polars

Goes extinct every 90 degrees when it rotates and shows birefringence

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Isotropic Behavior of Light

Light slows down uniformly and doesn’t split

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Anisotropic Behavior of Light

Undergoes double refraction, splitting unpolarized light into two perpendicular rays (fast and slow)

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Orientations Where Mineral Behaves Isotropically

Uniaxial and Biaxial

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Retardation

Distance that the fast ray is ahead of the slow ray

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Extinction

Anisotropic minerals go extinct (dark) every 90 degrees of rotation

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How to Identify Slow Ray

If color order rises after putting in the accessory plate

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How to Identify Fast Ray

If color order falls after putting in the accessory plate

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Pleochroism

Minerals exhibit changing body colors when viewed under plane polarized light as the stage is rotated

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Rules for Ordinary Ray (ω)

1.) Vibrates in 001/0001 plane

2.) Vibrates perpendicular to c axis

3.) Coincident with wave normal

<p>1.) Vibrates in 001/0001 plane</p><p>2.) Vibrates perpendicular to c axis</p><p>3.) Coincident with wave normal</p>
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Rules for Extraordinary Ray (ε)

1.) Vibrates perpendicular to ordinary ray

2.) Vibrates in a plane that contains the c axis and extraordinary ray

<p>1.) Vibrates perpendicular to ordinary ray</p><p>2.) Vibrates in a plane that contains the c axis and extraordinary ray</p>
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Optically Positive

Extraordinary ray is larger than the ordinary ray

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Optically Negative

Ordinary ray is larger than the extraordinary ray

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Prolate Spheroid

Football shape

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Oblate Spheroid

Frisbee shape

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Piercing Point

Construct the line perpendicular to the wave normal that strikes indicatrix as a tangent

<p>Construct the line perpendicular to the wave normal that strikes indicatrix as a tangent</p>
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Principal Section

High birefringence, largest difference between ordinary and extraordinary rays

<p>High birefringence, largest difference between ordinary and extraordinary rays</p>
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Circular Section

No birefringence, only the ordinary ray

<p>No birefringence, only the ordinary ray</p>
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Random Section

Intermediate birefringence

<p>Intermediate birefringence</p>
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Isochrome

“Rings” around isogyre

<p>“Rings” around isogyre</p>
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Isogyre

Cross looking thing

1.) Ordinary ray vibration direction is along latitudinal lines

2.) Extraordinary ray direction is along longitudinal lines

<p>Cross looking thing</p><p>1.) Ordinary ray vibration direction is along latitudinal lines</p><p>2.) Extraordinary ray direction is along longitudinal lines</p>
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Melatope

The center

<p>The center</p>
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Optically Positive Sign

1.) Extraordinary ray is slow

2.) Ordinary ray is fast

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Optically Negative Sign

1.) Ordinary ray is slow

2.) Extraordinary ray is fast

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<p>Definition of A</p>

Definition of A

Addition - Interference colors INCREASE

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Definition of C

Subtraction - Interference colors DECREASE

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Off-Centered Optic Axis


<p></p>
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Flash Figure


<p></p>
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Why does entirety of FOV go extinct for a flash figure?

It reorients lat/long