What is Color Rendering Index (CRI)?

Nov 10, 2017 | Glossary of Spectroscopy Terms, Properties of Light

The color rendering index is a way to quantify whether colors under a light source will look the same as in daylight. This is reflected (figuratively and literally) in the light source’s spectrum. A light source with a spectrum that is different than the sun will have...

What is light Intensity/Absolute Intensity/Irradiance?

Nov 10, 2017 | Glossary of Spectroscopy Terms, Properties of Light, StellarNet Definition

What is Light Intensity, Absolute Intensity, and Irradiance? Light intensity is commonly used to describe the amount of optical power falling on a given area. In spectroscopy and radiometry, the more precise term for this quantity is irradiance. Irradiance is defined...

What is a Numerical Aperture?

May 25, 2017 | Glossary of Spectroscopy Terms, Properties of Light

Numerical aperture is a measure of how many angles of acceptance an optic can accept. It is described by the following equation: where NA is the numerical aperture, n is the refractive index, and is the cone angle. Assuming the optic is in air (n=1), the numerical...

What is an Chromatic Aberration?

Mar 19, 2017 | Glossary of Spectroscopy Terms, Properties of Light, Spectrograph

Chromatic aberration is an aberration caused by dispersion. When a beam of light is transmitted through a lens, dispersion causes the wavelengths to focus at different focal points. The aberration can be corrected by adding other materials to essentially cancel out...

What is an Aberration?

Mar 19, 2017 | Glossary of Spectroscopy Terms, Properties of Light, Spectrograph

What is an Aberration? An aberration is an optical imperfection that causes an optical system to deviate from its ideal performance. In a perfect optical system, all light rays would be focused exactly where intended. In practice, lenses, mirrors, and other optical...

What is Refraction?

Mar 19, 2017 | Glossary of Spectroscopy Terms, Properties of Light

Refraction is when a light beam changes direction after entering a new medium. This is why objects in the water are seen at a different place from where they actually are; the light has been “bent” when exiting the water. The image below shows light being refracted...