A wave with low energy will also have long wavelengths and low frequencies.
The given in a single photon of a wave is given by Planck's equation: E = hc/λ and E = hf
Where λ is the wavelength and f is the frequency of the photon. This means that energy is directly proportional to the frequency and inversely proportional to the wavelength. Thus, it is visible that photons with a lower frequency and a longer wavelength will have a lower energy.
I would say long wavelengths and low frequencies due to the low energy. With less energy I would expect the wavelengths to be drawn out and with a low amplitude and also for low energy to get low frequencies ie waves passing by more slowly.