Multiple Rainbow Orders
November 27, 2012
When viewing rainbows we can often observe a secondary rainbow just to the outside of the primary rainbow. Two reflections inside a raindrop are required for a secondary bow to be visible. With a slide projector and a fine water jet, I created the six rainbow orders shown above. More orders are possible but to produce them a perfectly spherical water droplet is required. Note that the third and fourth orders are on the opposite side of the water jet from the primary and secondary bows. The fifth and sixth orders, however, are on the same side of the jet as are the primary and secondary bows. During a rain shower, under exceptional atmospheric conditions, it may be possible to observe a third order bow, but it would appear very dim – about a quarter as bright as the primary bow.