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.
Correlation between the absorption spectrum of protoporphyrin IX (PpIX) solution and exposure spectrum of the 3 types of light-emitting diodes (LEDs). PpIX has several peaks in the absorption spectrum (arrow). The blue band is markedly larger compared to the absorption band at 635 nm.
