Feb 14

Written by:
2/14/2012 1:53 PM 

What is Light refraction?

 

My favorite way to demonstrate refraction is to fill a clear glass partially with water, and

place a spoon upright in it. The spoon appears to be bent at water level. The appearance

of the spoon bending is caused by refraction of light. Every substance bends a ray of

light to a different degree. The comparison of how fast light travels through air, and

through the substance is expressed in its refractive index.

 

Example: Speed of light in air ( Y1 ) 300,000 km/sec

 

Speed of light in a diamond (Y2) 124,120 km/sec

 

Refractive Index = Y1 = 300,000 = 2.415

                                   Y2 124,120

 

Light travels 2.415 times faster in air than in a diamond. Most gems refractive index (RI)

are between 1.4 and 3.2. The higher the index, the more it bends light.

 

Most gems in jewelry have two Refractive Indexes. They are called doubly refractive. As

light enters these gems, it is refracted and is divided into two rays.

 

In our gem lab at Koser Jewelers, we measure refraction with a GIA Refractometer. In

the gem articles I write for our blog, I include the RI’s, Refraction Indexes. The higher the gem’s RI, the more fire and scintillation it will have.