Why is a rainbow arc-shaped?

Answer 1

Better yet why is the rainbow one of the symbols for gay pride? This makes no sense to me.

Answer 2

When we see rainbows we see them as arcs when in truth they are formed as circles. There is a point called the antisolar point that the rainbow seems to form around.

We don't see the full circle of the rainbow because the horizon gets in the way. As the sun goes down we are able to see more of the rainbow, and the higher the sun is in the sky the smaller the arc seems.

Sometimes people at high elevations, like in planes, see rainbows as full circles because they do not have the horizon to block their view.

Answer 3

Two physical phenomena are at work within a rainbow: refraction and reflection. Refraction occurs each time light passes across a boundary from one substance to another, such as from air into water. As light crosses that boundary, the rays bend at different angles depending on the wavelength (color) of light. This is the familiar prism effect wherein "white" sunlight is broken into a spectrum of different colors from red to blue-violet.

The same thing that happens in a rainbow: white sunlight enters a raindrop and is broken into different colors heading in slightly different directions. The light is then reflected (and magnified) off the back of the raindrop and passes back into the air again, in the process being further refracted.

For more detail check out:
http://www.photocentric.net/rainbow_physics.htm

Answer 4

good question. I went to wiki to get the answer.

"The rainbow's appearance is caused by dispersion of sunlight as it is refracted by (approximately spherical) raindrops. The light is first refracted as it enters the surface of the raindrop, reflected off the back of the drop, and again refracted as it leaves the drop. The overall effect is that the incoming light is reflected back over a wide range of angles, with the most intense light at an angle of about 40°–42°. This angle is independent of the size of the drop, but does depend on its refractive index. As seawater has a higher refractive index than rain water, the radius of a 'rain'bow in a sea spray is smaller than a true rainbow. This is visible to the naked eye by a misalignment of these bows"

I don't know if this is exactly what you're looking for, but you can go there and see the rest of the article for yourself.

Answer 5

like the previous post, the lephrechauns like their water theme park water slide or slip and slide and they put their pot of gold at both ends of the rainbow. be sure to slide into the rrr pot of gold. be sure when you get there to give me 50% of the gold.

the rainbow is planar, it is not spherical or 3D.

it is symbolic like Noah, from earth with the ark to above in the water which flooded the earth and then back to earth on a mountain. pretty kewl huh. So the ark is like an arc. Noah rode the arc of the rainbow, and yes like the previous post, it is a covenant with God and Noah - the human race is not to be judged by water again.

When you spray water with a hose with a cone shaped water emitted from the hose you don't see a rainbow sphere do you?

Haven't you seen a halo rainbow when clouds or water surround the sun? it is pretty kewl then you get a halo not a planar semi-circle of the rainbow.

Answer 6

The fundamental process at work in a rainbow is refraction -- the "bending" of light. Light bends -- or more accurately, changes directions -- when it travels from one medium to another. This happens because light travels at different speeds in different mediums.

Photo courtesy National Oceanic and Atmospheric Association

To understand why light bends, imagine you're pushing a shopping cart across a parking lot. The parking lot is one "medium" for the shopping cart. If you're exerting a constant force, the cart's speed depends on the medium it's traveling through -- in this case, the parking lot's paved surface. What happens when you push the shopping cart out of the parking lot, onto a grassy area? The grass is a different "medium" for the shopping cart. If you push the cart straight onto the grass, the cart will simply slow down. The grass medium offers more resistance, so it takes more energy to move the shopping cart.

But when you push the cart onto the grass at an angle, something else happens. If the right wheel hits the grass first, the right wheel will slow down while the left wheel is still on the pavement. Because the left wheel is briefly moving more quickly than the right wheel, the shopping cart will turn to the right as it moves onto the grass. If you move at an angle from a grassy area to a paved area, one wheel will speed up before the other and the cart will turn.

Similarly, a beam of light turns when it enters a glass prism. This is a simplification, but think about it this way: One side of the light wave slows down before the other, so the beam turns at the boundary between the air and the glass (some of the light actually reflects off the prism surface, but most passes through). The light turns again when it exits the prism, because one side of it speeds up before the other.

In addition to bending light as a whole, a prism separates white light into its component colors. Different colors of light have different frequencies, which causes them to travel at different speeds when they move through matter.

A color that travels more slowly in glass will bend more sharply when it passes from air to glass, because the speed difference is more severe. A color that moves more quickly in glass won't slow down as much, so it will bend less sharply. In this way, the colors that make up white light are separated according to frequency when they pass through glass. If the glass bends the light twice, as in a prism, you can see the separated colors more easily. This is called dispersion.

A prism separates white light into its component colors. For simplicity's sake, this diagram shows only red and violet, which are on opposite ends of the spectrum.

Drops of rainwater can refract and disperse light in the same basic way as a prism. In the right conditions, this refraction forms rainbows. In the next section, we'll find out how this happens.

Answer 7

that is completely ring formed. If seen from intense adequate contained in the air you may want to work out the entire circle. Being on the floor we purely see the arc. There are consistently 2 rainbows. One interior the different. the proper one is in many situations fainter and its colorations are contained in the opposite order of the different rainbow

Answer 8

Because that's the way God made it. It's a visible sign (reminder) of his covenant promise not to flood the world again. Go to the book of Genesis in the bible and look for the account of Noah.

It's actually a circle. On a sunny day go outside - get a hose - put your thumb over the hole enough to spray water like rinsing a car, etc... if you hold up the spray of water just right you can see a rainbow. Follow it around and you will see that it's a circle. :)

Answer 9

A rainbow is a hemisphere, but only visible in 2 dimensions.

Answer 10

It is al in the eye of the beholder, it really is circular but the earth gets in the way.

I was once in a helicopter flying through a rainstorm. We were surrounded at one point by THREE concentric rainbows, all perfectly circular. With us in the middle.