Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Each line indicates the wavelength of the test light quality. WL is white light, R4:B1 is red:blue ratio is 4:1; BL is blue light, R1:B4 is red-blue 1:4; RL is red light.
