GEM ID

Question 1

What is the Angle of incidence?

Answer 1

The angle at which a ray of light strikes a surface, measured from the normal.

Question 2

What is the angle of refraction?

Answer 2

The angle between the normal and a refracted light ray.

Question 3

What is Biaxial?

Answer 3

Doubly Double refractive with two optics axies.

Question 4

Birefringence is..

Answer 4

The numerical difference between a DR gem’s highest and lowest RIs.

Question 5

What is birefringence blink?

Answer 5

A method of determining birefringence that involves looking for a light-to-dark or green-to-red change in a spot.

Question 6

What is contact liquid?

Answer 6

Liquid that makes an optical contact between a refractometer hemicylinder and the material being tested.

Question 7

What is the critical angle?

Answer 7

An angle between the normal and the maximum angle of refraction.

Question 8

Explain doubling.

Answer 8

The appearance of double images of a gemstones features on the side opposite the viewer.

Question 9

Explain doubly refractive

Answer 9

Possessing different physical or optical properties in different crystal directions.

Question 10

What is Anisotropic?

Answer 10

It means double refractive

Question 11

What is an Extraordinary Ray?

Answer 11

The polarized ray that transmits through uniaxial stone with a varying RI

Question 12

What is a Hemicylinder?

Answer 12

A half cylinder in a refractometer, made of high lead, high -RI glass, on which a gem is placed.

Question 13

Explain monochromatic light

Answer 13

light that consists of only one wavelength and one hue.

Question 14

What is the ‘normal’

Answer 14

An imaginary line perpendicular to the point where a ray of light strikes the surface.

Question 15

What is an oblique angle?

Answer 15

Any line other than a right angle.

Question 16

What is an optic axis?

Answer 16

Direction of single refraction in a double refractive gem.

Question 17

What does ‘Optic character’ mean?

Answer 17

The number of optic axes in a doubly refractive stone.

Question 18

What is an ‘Optic Sign’?

Answer 18

Statement of the relationship between the Dr stones’ two RI’s.

Question 19

What is an ordinary ray?

Answer 19

The Polarised ray that transmits through a uniaxial stone with an RI that remains constant.

Question 20

What is OTL?

Answer 20

Description of a gem with an RI higher than that of the contact liquid.

Question 21

What is a Parallax?

Answer 21

Wavering of RI reading between scale divisions.

Question 22

Explain Polarization.

Answer 22

Limiting a light beam to one vibration plane that’s perpendicular to it direction of travel.

Question 23

Refraction is…

Answer 23

The change in speed and possible bending of light as it passes through one material to another.

Question 24

Refractive index is….

Answer 24

A measure of the change in the speed and angle of light as it passes from one material to another.

Question 25

What does a refractometer do?

Answer 25

An instrument that measures the critical angle of a gem and translates it directly to RI

Question 26

What does single refractive mean?

Answer 26

Possessing the same physical or optical properties in all crystal directions.

Question 27

What is another name for single refractive?

Answer 27

Isotropic.

Question 28

What does Uniaxial mean?

Answer 28

Doubly refractive with one optic axis.