City Plastics Light Transmission

The information on this page gives some details on light transmission of some standard grades of acrylic and polycarbonate sheet.

When light strikes acrylic or polycarbonate material, some light is transmitted, some reflected, and the rest absorbed. The light transmission depends on the reflectance at both surfaces and the absorption of light into the material.
Clear acrylic sheet absorbs less than 0.02% of visible light per millimetre of thickness. 
Reflected light occurs at both surfaces. A beam of light striking acrylic sheet perpendicular to the surface (at 0° angle of incidence) will lose approximately 4% at both surfaces due to reflection.
Due to the nearly zero absorption, the overall visible light transmission will be approximately 92%.

If light rays strike a sheet at angles of incidence greater than 30° from the vertical, the surface reflectance will be greater than 4%. The light transmission will thus be smaller. When light falls on acrylic sheet from all angles, as from a sky of uniform brightness, the transmission factor of visible light will be approximately 85%.

The following graph shows the light transmission curves of 3 materials, A-Cast acrylic sheet, Mitsubishi Shinkolite acrylic and Hyzod Polycarbonate sheet.

Items of interest are the wavelengths of various types of light.
UVC  100 - 290 nm
UVB  290 - 320 nm
UVA  320 - 400 nm
Visible light 400 - 700 nm

The harmful UV light that causes sunburn and sun tanning is UVA and UVB (290 - 400 nm)