In which portion of the electromagnetic spectrum is the maximum intensity of the earth outgoing radiation

Infrared is the region in the electromagnetic spectrum to which the maximum intensity of the earth's outgoing radiation.

To explain why it falls on the infrared region of the electromagnetic spectrum, it must be noted that solar radiation powers the climate system of the earth. Some of these are reflected by the Earth and its atmosphere. Now, the earth does not contain the sun's energy from within its vicinity. It gives off infrared radiation through its surface to maintain its internal temperature.