Explain rainbow formation?

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. Double Rainbow (outer arc on right) Let's pick a single raindrop in the BLUE band of the arc. The blue light is but one part of the spectrum of colors - each shining out from the raindrop at a different angle. Blue is shining our direction, but the other colors shoot out in different directions and therefore we can't see them from where we stand. Now look at an adjacent raindrop: it's also shining blue light at us. In fact, all of the nearby raindrops appear blue from where we're standing. But if we look at a single raindrop in the RED band of the arc, only the red light is shining our direction. In between blue and red, we find "all the colors of the rainbow" refracted and reflected from countless raindrops in just such a way that they shine our direction. Beyond the edge of the arc, where we see no color, the raindrops may be emitting colored light but none shines in our direction. Double Rainbow Photo by Bob Peavy Under certain conditions, some of the light will bounce off the inside of the water droplet more than once, exiting at a different angle. This produces a weaker, secondary arc known as a double rainbow. Bob Peavy has captured this phenomenon in the images above and left. Note the colors are reversed in the secondary rainbow. In theory there are additional rainbows (third, fourth) but those are too faint to see. read less

One of nature's most splendid masterpieces is the rainbow. A rainbow is an excellent demonstration of the dispersion of light and one more piece of evidence that visible light is composed of a spectrum of wavelengths, each associated with a distinct color. To view a rainbow, your back must be to the sun as you look at an approximately 40 degree angle above the ground into a region of the atmosphere with suspended droplets of water or even a light mist. Each individual droplet of water acts as a tiny prism that both disperses the light and reflects it back to your eye. As you sight into the sky, wavelengths of light associated with a specific color arrive at your eye from the collection of droplets. The net effect of the vast array of droplets is that a circular arc of ROYGBIV is seen across the sky. But just exactly how do the droplets of water disperse and reflect the light? And why does the pattern always appear as ROYGBIV from top to bottom? These are the questions that we will seek to understand on this page of The Physics Classroom Tutorial. To understand these questions, we will need to draw upon our understanding of refraction, internal reflection and dispersion. read less

A rainbow is an optical and meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc.The birth of each rainbow begins with millions of tiny rain droplets. The rain droplets serve as a type of reflector of light. White light enters one individual rain droplet and exits as one specific color of the spectrum. Without millions of rain droplets, a rainbow would not occur. If you only had a few rain droplets you would only see a few colors. This is typically why rainbow appear after a rain storm. Each rain droplet has a function in the formation of the rainbow. Sunlight enters the rain droplet at a specific angle and the rain droplet separates the white light into many different colors. This angle is a fixed measurement between your eye and the sun. What color is refracted depends upon the critical angle, which is the angle the sunlight strikes the back of the rain droplet. Red light bends the least, exiting the rain droplet at a 42 degree angle, while Violet light bends the most, exiting the rain droplet at a 40 degree angle. All of the other colors of the rainbow exit the rain droplets at some angle between 40 and 42 degrees, thus making up the colors of the rainbow ROYGBIV, this order never changes. read less

When light travels from one medium to another, it bends. In other words, it changes direction and moves at different speeds in different mediums. This property of light is called "refraction". We also know that white light is made up of different colours. Different colors of light have different frequencies. Except in vacuum and air, they travel at different speeds in different mediums. If you were to allow a beam of light to pass through a simple prism, it will bend when it enters the prism, when it leaves the prism it bends again. The different colours of the white light travel with different speeds inside the prism. The slanted surfaces of the prism makes the different colours emerge separately, thus in addition to bending light as a whole, a prism separates white light into its component colors. This splitting of light into its component colours is called dispersion, where prism is a dispersing element. This is exactly what happens when the sun rays hit droplets of water. When the sunlight strikes a raindrop, the light is refracted (bent) because the light is moving from one medium(air) to another( water). Drops of rainwater can disperse light in the same way as a prism.. When the light comes out of the water droplet, the sun's rays (white light)have now been split into their component wavelengths (colors). In this way, each individual raindrop behaves just like a prism, dispersing white sunlight into its seven component colors and a rainbow is formed. The rainbow we see is thus a result of many, many raindrops bending the sun's rays. read less

A rainbow is an optical and meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun. read less