In the case of harder X-rays,

Hard X-rays are characterized by their high penetrating power, which implies that the individual photons possess higher energy.

The energy of an X-ray photon is given by $E = h\nu = \dfrac{hc}{\lambda}$, where $\nu$ is the frequency and $\lambda$ is the wavelength.

For harder X-rays, the photon energy $E$ is higher. Consequently, the frequency $\nu$ is higher and the wavelength $\lambda$ is shorter.

The intensity of X-rays depends on the number of photons emitted per second and is independent of the hardness of the X-rays.