Chatpter 8 Luminescence and UV Light

Luminescence and UV Light (1)

What are Luminescence effects?

The emission of ‘cold’, non-incandescent, visible light by a substance.

What are Incandescent effects?

Light that is not produced by heat.

What is Fluorescence?

The emission of visible light by a substance whilst it is being excited by radiation of higher energy (shorter wavelength).

What usually provides the excitation for fluorescence?

Visible light, UV-Light, and X-rays.

What is Phosphorescence?

Radiation emitted by a material irradiated by a higher-energy source, occurring during and AFTER the removal of the source irradiation.

Where does UV light appear on the electromagnetic spectrum?

Between 10nm and 400nm. Between X-rays and visible light.

What is the wavelength of Long Wave UV (LWUV) light?

365nm; most convenient for daily use.

What is the wavelength of Short Wave UV (SWUV) light?

254 nm; higher energy and can be harmful.

What is UV Light used for in gemmology?

Back up to already made observations,

indicate the direction of further testing,

separating or sorting rough and cut stones,

gem material prospecting.

Give an example of the use of UV light to distinguish gem materials.

Diamonds fluoresce blue (green, orange, yellow under LWUV),

Cubic Zirconia fluoresces orange/yellow under SWUV.

What types of luminescence are there

fluorescence and phosphorescence