Rainbow where is the sun

Light enters a water droplet, bending as it slows down a bit going from air to denser water. The light reflects off the inside of the droplet, separating into its component wavelengths—or colors. When it exits the droplet, it makes a rainbow. Sunlight is made up of many wavelengths—or colors—of light. Some of those wavelengths get bent more than others when the light enters the water droplet.

Violet the shortest wavelength of visible light bends the most, red the longest wavelength of visible light bends the least. So when the light exits the water droplet, it is separated into all its wavelengths. The light reflecting back to you, the observer with the Sunlight coming from behind you, from the water droplets will appear separated into all the colors of the rainbow! Violet will be on the bottom and red on the top.

A secondary rainbow appears if the sunlight is reflected twice inside the water droplets. Secondary rainbows are fainter, and the order of the color is reversed, with red on the bottom. Furthermore, neither one can be seen from the back side, i. This point brings up other interesting questions. Can't some of the sunlight pass through the back side of the water droplet without being reflected? Wouldn't this light be visible from behind the rainbow? The answers are yes and yes.

Although it is only a small amount, some of the sunlight that enters a mist droplet indeed continues through the back side without being reflected. Therefore, if you were to walk to the other side of the cloud of mist that is creating the rainbow and turn around, you would indeed see a pattern of light if the viewing conditions are favorable. However, it would not be a rainbow. It would be a pattern called an "atmospheric solar corona", as shown below.

A solar corona still includes an arcing shape and a spread of colors, but the size and color sequence of a solar corona are different that of a rainbow. Since most of the sunlight that enters the mist droplet is reflected and not transmitted through, rainbows are very bright and common while solar coronas are dim and rare. Additionally, since you are behind the rainbow, you are now looking directly toward the sun.

Different colors have slightly different minimum deviation angles, hence the brightness for each colored arc of the rainbow. Ray diagram for sunlight refracting twice and reflecting once in a raindrop. The exit angles of the rays from the raindrop condense along the minimum deviation angle of degrees.

Adam, Physics Reports, The light inside in the arc of the primary rainbow i. The index of refraction of a given medium equals the speed of light in a vacuum divided by the speed of light inside that medium. Light slows down inside denser media. This means the index of refraction for everything but a vacuum is greater than 1. In the diagram above, light bends towards the normal 2 The normal to a surface is a vertical line perpendicular to the surface to the surface shown by the vertical dashed line as it enters the water.

The colors of white light separate in the raindrop due to dispersion , resulting from the wavelength dependence for the index of refraction. Blue light refracts more than red. Inside the raindrop, some light reflects from the rear surface of the raindrop. Some of this reflected light exits the front surface of the raindrop.

As this light exits the raindrop, it refracts again since it leaves a denser media water into a less dense medium air and therefore bends away from the normal to the surface of the raindrop. The index of refraction for different wavelengths of light color is listed here. Violets and blues have a higher index of refraction than reds, and therefore violet refracts more bends more than red. When light crosses from one medium to another it refracts bends. The amount of refraction depends on the angle of incidence on the media interface and the wavelength color of the light.

Shorter wavelengths purples and blues refract bend more than longer wavelengths oranges — reds. This effect accounts for the width of the rainbow with redder colors on the outside of the primary rainbow and blues and purples being on the inside of the bow.

Note that different raindrops direct a specific color to our eye i. Inside the raindrop, some of the light reflected from the back surface reflects one more time from the front inner surface of the raindrop. See the dashed rays in the figure below. Double rainbow outside of Santa Fe, New Mexico. Anti-crepuscular rays can be seen converging to the anti-solar point. The light rays that form a double rainbow are shown here by dashed lines.

These rays undergo two reflections inside the raindrop before they exit the drop at 51 degrees from the anti-solar point the shadow of your head. The second reflection reverses the colors in the secondary bow from the order of colors in the primary bow.

Note how different rays of sunlight reach our eyes from the primary rainbow and secondary rainbow. Light rays that lie between the primary rainbow angle of degrees and the secondary rainbow at degrees cannot be refracted back towards the viewer due to the concept of total internal reflection. These rays cannot make it out of the raindrop.

Light propagating from inside a medium with a higher index of refraction to a medium with a lower index of refraction can only make it out of the material for a given range of angles. You can see this effect in double rainbows as the dark band between the two rainbows.

If you look closely at the above ray-tracing diagram, you can see that different light rays produce the primary and secondary rainbow. Thinking about the angles involved, you realize that the raindrops which produce the secondary rainbow are different from the raindrops that produce the primary bow.

The raindrops responsible for the secondary bow are at an angle of degrees from your shadow, whereas the raindrops associated with the primary bow are at 42 degrees. Note the shadow of my camera on the tripod at the center of the rainbows — my camera is the anti-solar point at the center of the rainbow arc. The colors in the secondary rainbow are reversed from the primary rainbow due to the extra internal reflection inside the raindrop for rays that form the secondary rainbow.

The width of the color band in the secondary rainbow is wider than the primary rainbow.