critical wavelength: The free-spacewavelengththat corresponds to thecriticalfrequency. Note: Thecritical wavelengthis equal, in meters, to the speed of light (3 × 108m/s) divided by thecriticalfrequency in hertz

critical wavelength:The free-spacewavelengththat corresponds to thecritical frequency.Note:The critical wavelength is equal, in meters, to thespeed of light(3 × 108m/s) divided by the critical frequency inhertz.

This HTML version of FS-1037C was last generated on Fri Aug 23 00:22:38 MDT 1996

90% of the area under the absorbance curve

critical wavelength:The free-spacewavelengththat corresponds to thecritical frequency.Note:The critical wavelength is equal, in meters, to thespeed of light(3 × 108m/s) divided by the critical frequency inhertz.

The wavelength at which the summed absorbance reaches 90% of total absorbance is defined as the 'critical wavelength' and is considered to be a measure of the breadth of sunscreen protection. Filters are then classified as 'broad spectrum', having a significant part of their absorbance in the UVA, when the critical wavelength is longer than 370 nm.

Thewavelengthat which the summed absorbance reaches 90% of total absorbance is defined as the 'critical wavelength' and is considered to be a measure of the breadth of sunscreen protection.