When the wavelength of a wave increases, the frequency decreases. The wavelength and frequency of a wave are inversely proportional to each other, meaning that as one increases, the other decreases.
Frequency refers to the number of wave cycles that pass a given point per unit of time. If the wavelength increases, it means that each wave cycle occupies a longer distance, and therefore fewer cycles will pass a given point in a given amount of time. As a result, the frequency decreases.
Amplitude, on the other hand, refers to the maximum displacement or intensity of a wave. It is not directly affected by changes in wavelength. The amplitude of a wave can remain the same regardless of changes in wavelength or frequency, as long as the properties of the medium through which the wave is traveling remain constant.
To summarize, when the wavelength of a wave increases, the frequency decreases, but there is no direct effect on the amplitude of the wave.