None of the properties of a wave are changed by diffraction. The wavelength, frequency, period and speed are the same before and after diffraction. The only change is the direction in which the wave is travelling.

What happens to the speed and wavelength in diffraction?

The amount of diffraction (the sharpness of the bending) increases with increasing wavelength and decreases with decreasing wavelength. In fact, when the wavelength of the waves is smaller than the obstacle, no noticeable diffraction occurs.

What effect does diffraction have?

Diffraction effects from circular apertures have an important practical consequence: the intensity patterns in optical images produced by circular lenses and mirrors are limited in their ability to resolve closely spaced features.