Rainbows live in two degrees of angle.

When Sir Isaac Newton’s dog overturned a candle which totally destroyed the only copy of the almost-finished manuscript of his great work ‘Opticks’…it took him 12 years to rewrite it. No wonder he had such a nasty disposition! His work on light and what happens to it as it passes through a prism helped explain such phenomena as rainbows.

Rainbows are seen when the sun is at your back and it is raining in front of you. Light from the sun strikes the water droplets and is refracted at the surface, the violet (shorter wavelength) light being bent more than the red. By the way, an easy way to remember the main colours of the rainbow is ‘Roy G. Biv’ (Red, Orange, Yellow, Green, Blue, Indigo, Violet). All the colours in their now separated state, carry on and are reflected off the back of the inside of the droplets and are again refracted as they go through the front surface.

From where you are standing (or moving) observing the rainbow, you can be absolutely certain that the angle made between you, the droplet and the sun is 42 degrees as you see the red droplets, and at the other side of the rainbow, it is a 40 degrees angle off the violet droplets, so that’s why the rainbow appears to keep up with you as you travel along. From an aircraft, the rainbow appears circular with the plane’s shadow in the centre of the circle. Ain’t physics wonderful!

To change the subject slightly, what happens to light and colour when one dives deeper and deeper into the ocean?  Well, the light becomes more diffuse… so shadows disappear… and the colour is increasingly washed out of the spectrum from the red end as the depth increases. Since reds are gone, to cut oneself is to see some sickly-coloured liquids leaking out. In extremely clear water, one can see the light sparkling on the surface 50 metres above.