Fresnel lenses at Pt. Reyes Lighthouse!A Fresnel lens is a type of lens invented by Augustin-Jean Fresnel.
A "fresnel" is also a unit of frequency.
from Wikipedia
Pt. Reyes Lighthouse - 12 miles out in the ocean!300 Steps down! And up!!
Fresnel lenses at Pt. Reyes Lighthouse!
Pt. Reyes Lighthouse - 12 miles out in the ocean!