Basics of Light
What is the term for the bending of light as it passes from one medium to another?
Refraction
What optical property makes a diamond sparkle?
Brilliance
Which angle causes light to reflect back entirely into a gemstone?
Critical Angle
What gemstone exhibits pleochroism?
Tanzanite
What is birefringence, and which gems exhibit it?
Double refraction of light; seen in calcite, zircon
What is the speed of light in a vacuum?
Approximately 299,792 kilometers per second
What is the approximate refractive index of diamond?
~2.42
What term describes a gemstone’s ability to reflect light back to the viewer?
Brilliance
What is the cause of the blue color in tanzanite?
Heat treatment enhances its natural pleochroic colors
What is an inclusion, and how does it affect light movement through a gem?
An internal feature that can scatter or block light
What part of the electromagnetic spectrum is visible to the human eye?
Visible Light
What is dispersion, and how does it affect a gem’s appearance?
Dispersion is the separation of light into colors; it creates "fire" in gems
What is total internal reflection, and why is it critical in gemstone cutting?
It’s when light reflects entirely within the gem instead of exiting; it increases sparkle
What is chatoyancy, and in which gems is it observed?
Cat’s eye effect seen in chrysoberyl, tiger’s eye
How does fluorescence in diamonds affect their appearance under UV light?
They may glow, often blue, which can affect appearance in some lighting
What is the term for the bouncing of light off a surface?
Reflection
What gemstone has one of the highest natural refractive indices?
Diamond
Why is the angle of the pavilion important in diamond cutting?
It affects how light reflects and exits, influencing brilliance and fire
What optical effect causes a star-like pattern in star sapphires?
Asterism
How does light absorption relate to a gem’s color?
A gem’s color is due to the wavelengths of light it absorbs and those it transmits
What causes a prism to separate white light into a spectrum of colors?
Dispersion
What causes the "fire" seen in diamonds?
Dispersion of light
How does a cabochon cut differ from a faceted cut in terms of light reflection?
Cabochons have a smooth, rounded surface and do not reflect light like facets
What is the name of the effect seen in opals where they display a play-of-color?
Opalescence or play-of-color
Which optical phenomenon causes labradorite to show a play of colors?
Labradorescence