Seems like I’ve been getting a lot of questions lately about both crepuscular rays and silver linings on clouds. Scan the recent archives and you’ll see what I mean. Both of these magnificent phenomena have been explained in previous columns, so if you need a review, just go back and check them out.
I thought I’d take a more general approach here. This image was captured during our July monsoons, and happens to show both effects quite nicely. We got some colors later, but at this point it was pretty much all white and silver.
As was explained in Why Most Sunsets are Red, light from the sun consists of all colors in the spectrum. In their mixed state, human eyes perceive the overall color as white. It’s only when some optical process intervenes (refraction, dispersion, interference) that the colors are separated, often producing spectacular effects.
But as you see, even white light can produce beautiful effects. All you need is the correct Sun and cloud positions to get shadows (crepuscular rays) and forward scattering (silver linings). Shadow formation and scattering are, of course, also optical effects, but they act on all colors of light more or less equally.