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Himal kharel
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why is rainbow always an arc?
Because the water drops are round.Himal kharel said:why is rainbow always an arc?
Har har. No.*A.T. said:Because the water drops are round.
And why is it 42 degrees in every direction from anti-solar point? Where is that symmetry coming from? Would the rainbow be still a circular arc, if the raindrops where ellipsoids, scaled by the factor 2 vertically?DaveC426913 said:You will find that a rainbow's centre point is always exactly opposite the sky from where the sun is, offset by an angle of about 42 degrees.
In fact raindrops are not spherical - they are oblate ellipsoids, flattened vertically by air resistance. More accurately, they are said to resemble the top half of a hamburger bun.And why is it 42 degrees in every direction from anti-solar point? Where is that symmetry coming from? Would the rainbow be still a circular arc, if the raindrops where ellipsoids, scaled by the factor 2 vertically?
I think it's save to assume that the OP is aware that there are multiple arcs, not just one. He seems to be asking about the reason for the circular shape.HallsofIvy said:It's not, exactly. Each color is refracted at a slightly different angle, depending on the wavelength (and size of rain drop but all raindrops are rougly the same size). But the angle for all wavelengths of visible light are about 42 degrees.
Nothing it perfectly spherical in nature. But how would the rainbow look like, if they were strongly flatten, say by a factor of 0.5?Bill_K said:In fact raindrops are not spherical - they are oblate ellipsoids, flattened vertically by air resistance. More accurately, they are said to resemble the top half of a hamburger bun.
A.T. said:Nothing it perfectly spherical in nature. But how would the rainbow look like, if they were strongly flatten, say by a factor of 0.5?
Of course it does, as A.T said. the arc nature of rainbow is caused by circular symmetry of a droplet.DaveC426913 said:I can't be sure but I don't think it would make a difference.
ProTerran said:@DaveC426913
Of course it does, as A.T said. the arc nature of rainbow is caused by circular symmetry of a droplet.
Lecture on rainbows:
ProTerran said:the arc nature of rainbow is caused by circular symmetry of a droplet.
Ice crystals have some symmetry too (hexagonal). But due to their asymmetries they also produce "sun dogs" (bright spots) or "light pillars":DaveC426913 said:Soooo how do you explain rainbows from ice crystals
A.T. said:Ice crystals have some symmetry too (hexagonal). But due to their asymmetries they also produce "sun dogs" (bright spots) or "light pillars":
[PLAIN]http://www.freewebs.com/sundiggitydog/diagram%20les%20cowley2.png
http://www.freewebs.com/sundiggitydog/sundogs.htm
The circular shape in the case of the ice crystals comes from their random orientation, not their shapeProTerran said:Answering your question regarding crystals the explanation is imo quite simple: the same rule applies to crystals, they also must have circular symmetry.
A.T. said:1) Why isn't it sometimes something else than an arc?
Answer: The spherical symmetry of the drops makes sure that orientation is irrelevant, and the effect is always an arc.
The shape of a rainbow is determined by the way that light is refracted, or bent, as it passes through water droplets in the air. The light is separated into its component colors, creating the arc shape that we see.
The arc shape is a result of the angle at which we view the rainbow. If we were able to see a rainbow from above or below, it would appear as a full circle. However, from our perspective on the ground, we can only see the upper half of the circle, creating the arc shape.
Yes, a rainbow can appear as a full circle if it is viewed from a high enough vantage point, such as an airplane or a mountain top. This allows us to see the full circle of light and water droplets, rather than just the arc shape from the ground.
The size of a rainbow's arc can vary depending on the size and position of the water droplets in the air. Thicker or larger droplets can create a larger arc, while smaller droplets may create a smaller arc. The position of the sun and the angle at which we view the rainbow can also affect the size of the arc.
In addition to the size and position of the water droplets, other factors such as the amount of light, the presence of other atmospheric particles, and the location of the observer can also impact the shape of a rainbow. These factors can create variations in the intensity, brightness, and even the appearance of multiple rainbows in the sky.