How are wavelength and frequency of a wave related?

The product of

(wavelength) x (frequency)

is always the same number. It's the speed of the wave.

So if either number changes, the other will always change by the

same factor in the opposite direction, in order to keep their product

constant.

Wavelength is the length from one peak of a wave to the next, while frequency is the amount of waves present in a unit of time. The greater the wavelength the smaller the frequency. The smaller the wavelength, the bigger the frequency.