Fog Bow

Saw a fog bow this morning.  It has a lot of similarities to a rainbow: it's formed because of light hitting suspended water droplets, always appears in the opposite direction from the sun, and the empty space inside the arc is always a bit lighter than the space outside of the arc.  Fog droplets, though, are hundreds of times smaller than rain droplets.  Light hitting a rain droplet is reflected internally and refracted out into colors.  In the tiny fog droplets though there is also diffraction spreading which broadens the angular band of each color so they overlap -  creating a broad white arc.   This process will cause the fog bow to appear a bit smaller than a rainbow and w/ a thicker bow.  Fog bows form when a strong light (the sun) shines on a thin fog bank (so the light can get through).   Sometimes a fog bow will appear quite dramatic.  Other times, it's so ethereal you have trouble believing that's what you are seeing.   It's a phenomena that is fun to look for and wonderful when you realize you've found it.