A rainbow is a full circle, but we see only part of it

By Richard Brill

POSTED: 01:30 a.m. HST, Mar 01, 2013

~~<p>Rainbows are both beautiful and rare, but we see more than our fair share of them in Hawaii because our mountains and tradewinds combine to produce rain on the slopes of the mountains. Because of the orientation of the islands, it is not unusual for the low morning or afternoon sun to shine under clouds over the mountains and illuminate rain beneath the clouds.</p>
<p>Rainbows are visible when a bright light source is directly behind an observer who is looking into airborne water droplets. The spectrum of colors appears in a circle around the observer's shadow. We see neither the shadow if the rain is far away, nor the entire circular spectrum when the sun is above the horizon. The sun must be no higher than 42 degrees or the light from the water drops does not reach the ground.</p>
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Rainbows are both beautiful and rare, but we see more than our fair share of them in Hawaii because our mountains and tradewinds combine to produce rain on the slopes of the mountains. Because of the orientation of the islands, it is not unusual for the low morning or afternoon sun to shine under clouds over the mountains and illuminate rain beneath the clouds.

Rainbows are visible when a bright light source is directly behind an observer who is looking into airborne water droplets. The spectrum of colors appears in a circle around the observer's shadow. We see neither the shadow if the rain is far away, nor the entire circular spectrum when the sun is above the horizon. The sun must be no higher than 42 degrees or the light from the water drops does not reach the ground. Login for more...