critical wavelength definition
Zinc oxide is the only single active ingredient allowed here in the US that offers full UVA and UVB protection. See chart below. Critical Wavelength and UVA Protection. The critical wavelength is the wavelength at which the sunscreen allows 10% of the rays to penetrate.A sunscreen with a critical wavelength over 370nm is considered by the FDA to provide excellent UVA protection.Badger sunscreens have critical wavelengths ranging from 379nm to 383nm, offering excellent protection from UVA rays!inc oxide is the only single active ingredient allowed here in the US that offers full UVA and UVB protection. See chart below. Critical Wavelength and UVA Protection. The critical wavelength is the wavelength at which the sunscreen allows 10% of the rays to penetrate.