The earth radiates in the infra-red region of the spectrum. The spectrum is correctly given by:

Wien's Displacement Law (${\lambda }_{m}T=\text{constant}$) relates the temperature of a body to the peak wavelength of its radiation spectrum. Since the Earth's temperature is relatively low (around $300\text{K}$), the peak of its radiation falls in the long-wavelength infrared region, as described by Wien's law.