Weight of Rainbow

For a maths homework task, we had to write a method to find the weight of a rainbow. How silly is what everyone first though but iof course homework is compulsory so, I came up with the idea that: On a very sunny day, I could run a hose with a sprinkler on the end and when I see a rainbow appear, shout to my friend to place a measuring jug under the spray of water and collect it for n seconds. I could guesstimate the median length of the arc and the depth, and then guesstimate the area. I could then look at the amount of water collected and divide this by the surface area of the rainbow to give the weight of 1m2of a rainbow.
What do you think?
- Carys (age 14)
Sidcup, Kent, England

Of course the problem with the question is that its meaning is not clear. You’ve tried to interpret it in a way to make some sense out of it, asking what weight of water is needed to make a visible rainbow. That’s very reasonable. Someone else might take it to mean the weight of the light rays , but that would give a weird answer that involves weight per time- and very small weights.

Mike W.

(published on 10/22/2007)

Why does indigo not belong to the colors of the rainbow?
- melvin (age 16)
General santos City, Philippines

We have three different types of cone cells to detect light colors. Each is triggered more by some frequencies of light than by others. The different color sensations represent different combinations of signals from the three different cone cell types.The colors of the rainbow represent the  whole range of visible frequencies, but only one frequency per color. Some combinations of cone signals just can’t be reached with any single frequency. An example would be  lots of signal from the cones which pick up low frequency and the ones which pick up high frequency but little signal from the ones which pick up middle frequencies. I guess indigo is one of the many colors which can’t be made from any one frequency.

Mike W.

(published on 02/01/2008)