Question

How do you calculate the frequency of red light?

Answer 1

Tricky, what we can state is that it is related to wavelength (normally quoted in the question) by the speed of light (given in the data sheet for exams.)

Explanation:

Most humans cannot see light above about 750 nm, and below 620 nm or so most people “see” orange. If we take these two values, we can find an answer ... using the wave equation.

`v = f xx lambda` (where the funny symbol, `lambda` means wavelenth in metres)

So `f = v/lambda`

`f_max = (3xx10^8)/(620xx10^-9) = 4.84xx10^14` Hz

`f_min = (3xx10^8]/(750xx10^-9) = 4xx10^14` Hz

So we can say the frequency lies between `4` and `4.84xx10^14` Hertz i.e. an extremely narrow range, showing just what a marvellously precise evolutionary structure the human eye is.

Not too bad, eh?