Rainbows are formed when sunlight is scattered from raindrops into the eyes of an observer.<br /><br />Most raindrops are spherical rather than the often depicted 'teardrop' shape and it is this spherical shape that provides the conditions for a rainbow to be seen.<br /><br />The position of the sun and the raindrops in relation to the observer need to be just right for a rainbow to form:<br /><br />- The sun needs to be behind the viewer<br /><br />- The sun needs to be low in the sky, at an angle of less than 42° above the horizon. The lower the sun in the sky the more of an arc of a rainbow the viewer will see<br /><br />- Rain, fog or some other source of water droplets must be in front of the viewer<br /><br />The size of the raindrops does not directly affect the geometry of a rainbow, but mist or fog tends to disperse the effect more (see fogbows).<br /><br />Rainbows only appear semi-circular over level ground at sunrise or sunset, when the sun is exactly on the horizon, the majority of the time a smaller segment of an arc is seen.<br />
