# Tag Info

### Why can't thin clouds form rainbows?

Clouds are complicated. There are lots of different types of clouds, which may be composed of spherical or non-spherical water droplets, with uniform or non-uniform sizes; planar or columnar ice ...
• 91.6k
Accepted

### Huygens' principle and the laws of reflection/refraction

The construction you link to shows the same wavefront at multiple points in time, not a snapshot of a light wave at one point in time. The yellow dots constituting the point sources at the interface ...
• 99

### Why can't thin clouds form rainbows?

You only see a bright, first-order rainbow when you are looking toward rain or mist and the Sun is behind you. Also, You said, "Sunlight easily passes through thin layers of cloud." That ...
• 15.2k

### Huygens' principle and the laws of reflection/refraction

The points shown as yellow blobs on your diagram are in phase, even though they are not on the same wavefront. The hemispheres drawn in the lower medium do seem like Huygens secondary wavelets. But ...
• 36.1k
1 vote

### Why can't thin clouds form rainbows?

As hinted at in the last paragraph of @rob's answer, cloud droplets are simply too small to achieve the diffraction-limited angular resolution needed for the color bands to be distinguishable. ...
• 6,176
1 vote

### The angle of the prism for which there is no emergent ray will be, if its critical angle is $i_c$?

You are right. There is an error in the linked answer. The first two equations should be: $\sin(i) = \mu \sin(r1)$ $\sin(e) = 1/\mu \sin(r2)$ The ratio $\mu = (N2/N1)$ has to be inverted for the ...
• 6,207
1 vote

### Most generic form of refractive index tensors

Symmetry: In non-magnetic media, the real part of the refractive index tensor is typically symmetric due to energy conservation principles. This symmetry is related to the reciprocity theorem in ...
• 21

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