In a maths lesson I was distracted by this rainbow out of the class window. I wondered what maths makes the shape of a rainbow? Rainbows are all to do with angles. How you see a rainbow depends on where you are standing near the sun. Everyone sees a different rainbow depending on where they stand. So sometimes you see a semicircle and sometimes only part of the rainbow. Rainbows happen when the sunlight refracts in raindrops which slows down different wavelengths of light and splits them up into different colours. Light also reflects off the spherical raindrop at 42 degrees which makes a circle but because we are not in the air we only see a part of the circle, an arc — the shape of the rainbow.
