Optical Properties

Light

• Electromagnetic radiation

• Wave or particle (photon)

• Red: 700 nm

• Blue: 400 nm

Reflectivity

% of incident light that is reflected by the materials surface

Absorptivity

% of incident light that is absorbed by the material

Transmissivity

% of incident that is transmitted through the material and exits on the other side

Opaque

• T = 0

• does not allow light through

Transparent

• T ≠ 0

• Can Cleary see image on other side

Translucent

• T ≠ 0

• Image on the other side is blurry

UV / Vis Spectroscopy

• A technique to measure the wavelength dependence of RAT

• Vary indent wavelength, measure absorption / reflection at each incident wavelength

  • High R / Low A: Color we see

  • High A / Low R: Color we don’t see

Surface Roughness

• Light beams reflect off of a rough surface in different directions due to surface roughness

• Give off “blurry” effect on water

Refractive Index (n)

• Materials property

• The ratio of the velocity of light in vacuum to the velocity of light traveling in a material

  • Light actually slows down a material

  • Vm = c / n

• The higher the index, the more light is slowed down, so it gets bent more, and the image is shifted more compared to a material with lower refractive index

Angle of Refraction

• Performance parameter

• Given by Snell’s law

  • n1sinθ1 = n2sinθ2