Assume that a light source, such as a laser, supplies 100000 photons per second in a specific wavelength band. What optical density does an optical filter need to have to reduce the photon flux rate...

Assume that a light source, such as a laser, supplies 100000 photons per second in a specific wavelength band. What optical density does an optical filter need to have to reduce the photon flux rate in this wavelength band to 20 photons per second?

The absorbance of a liquid sample of a fluorophore was determined to be 0.425. What percentage of the light received by the sample was absorbed by the sample?