How is the cause of cloud iridescence physically distinct from that of a traditional rainbow?

Answer

Iridescence uses diffraction around particles, whereas rainbows are caused by refraction and reflection within individual raindrops.

A rainbow is distinct from iridescence because the rainbow phenomenon is caused by the refraction and reflection of light within individual raindrops, whereas iridescence is caused by the diffraction of light around cloud particles.

How is the cause of cloud iridescence physically distinct from that of a traditional rainbow?
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