Water Droplet Diffraction

To make the distinction between diffraction and refraction effects in the atmosphere, consider what size droplet would be necessary to produce diffraction at 22° to coincide with the 22° halo.

While very small, the particle size to produce a maximum at 22° is conceivable, but the effect would be quite different from the 22° halo. The colors of the visible spectrum would be spread from about 18 to 30 degrees. The normal corona around the Sun is more like 10°, corresponding to a particle size on the order of 6 micrometers.