Yes, a wave can still have a frequency and wavelength even if its amplitude is very small or zero. The frequency of a wave refers to the number of complete oscillations or cycles the wave undergoes per unit of time. It is typically measured in hertz (Hz), which represents the number of cycles per second.
The wavelength of a wave, on the other hand, is the distance between two consecutive points in the wave that are in phase, or the distance it takes for one complete cycle to pass. It is commonly represented by the Greek letter lambda (λ) and is usually measured in units such as meters (m) or nanometers (nm).
The amplitude of a wave represents the maximum displacement or magnitude of the wave from its equilibrium position. It is a measure of the wave's intensity or energy. If the amplitude of a wave is very small or zero, it means that the wave is very weak or effectively non-existent. However, the frequency and wavelength of the wave are independent of its amplitude.
In fact, in the case of electromagnetic waves, such as light, the energy carried by the wave is proportional to the square of its amplitude, but the frequency and wavelength remain unchanged regardless of the amplitude. This means that even if the amplitude is extremely small, the wave can still have a well-defined frequency and wavelength.