We know that a rainbow is an arc of "pure spectral colors". Originally, Sir Isaac Newton described only five primary colors, later he increased the number to seven. The colors of the rainbow include red, orange, yellow, blue, green, indigo, and violet. These colors appear in the sky opposite the sun and they are caused by the refraction and reflection of the sun´s rays through rain droplets or mist in the sky.
Rene Descartes, as the undisputed father of modern philosophy, is perhaps the most famous "researcher of rainbows". He is credited with proving the law of refraction or Snell´s Law. The law of refraction is a formula used to describe the relationship between refraction and the angles of incidence. We know that sunlight bends (refracts) as it enters the surface of the rain or mist in the air. Some of the light passes through the rain and some is reflected back off the raindrop and finally, refracted again as it leaves the drop. The light effect that we see is the reflected light over a range of angles, with the most intense light at an angle of 40º - 42º.
While Descartes is probably the most well-known rainbow specialist, al Hassan Ibn al-Haytham is certainly the least well-known scientist. Born around 965 in present-day Iraq, al-Haytham is thought to have initially established the modern scientific method long before Francis Bacon and Rene Descartes. If Descartes is known as the father of modern philosophy, Ibn al-Haytham is considered the "father of optics¨. In fact, according to some, he is considered the "world´s first true scientist".
What makes a double rainbow?
What are supernumerary arcs?
Can you see Rainbows at Night?
- A double (or secondary) rainbow is somewhat rare. It is caused by a double reflection of sunlight inside the drops of rain. The main difference is that the dispersed light is reflected twice within the raindrop before it exits. This makes the colors appear at an angle of 50º- 53º. As a result of this second reflection, the colors are inverted with blue on the outside and red on the inside.
- This is a very rare phenomenon.A supernumerary consists of several faint rainbows on the inner side of the primary rainbow. These "multi" rainbows are evidence of the wave nature of light and it is caused by interference of reflected light that travels along different paths inside the rain drop.
- Well..we know that the sun is responsible for the majority of the rainbows that we see. However, there are Lunar Rainbows that occur when light is reflected off the moon´s surface .The colors of a moonbow are normally very faint and often appear white to the human eye.
Rainbow Experiments and Lesson Plans