Why are rainbows always in the shape of an arch?

Answer 1

Hi. The droplets which split the light into the spectrum in a rainbow are spherical, so the reflection is a section of a sphere, a circle. A straight prism gives a "rainbow" that is also straight.

Answer 2

Actually, it is a circular arc. This is because the droplets are uniformly scattered, and the angle of refraction, for a particular-color ray of light, headed towards the eye of an observer, from a particular single water drop, depends on the angle of the incident white light upon the drop, and the drop's position with respect to the observer, on the ground. Remember, the incident white light is comprised of parallel rays, but the drops, with respect to the observer, are in different positions. Knowing the refractive index of water, the position of a single observer, and the wave lengths of the different colors of light; the shape of the rainbow can be calculated, mathematically, and proved to be a circle. Remember, the rainbow occurs due to refraction of white light through the water droplets, and NOT due to diffraction, please. Diffraction takes place around the edges of a solid object, such as the diffraction fringes formed during a solar eclipse, due to the intervening moon.

Answer 3

Because rainbows are caused by a refraction of light in the atmosphere off of rain drops; the rainbow will appear when the angle between the raindrops and the sun is at a certain angle--in order to maintain this angle, the rainbow must curve as we observe.

Answer 4

Rainbows are caused by light diffracting through the atmosphere. This actually occurs in a huge circle, but rarely do we see the entire circle. We see just the arc of the circle.

Answer 5

You can see circular rainbows even from a helicopter or plane.

Answer 6

they are actually circular, but you can only see half from ground level. if you went into space you would see a circle on the planets surface.

Answer 7

because the earth is round