1. By the Wien Law,
| Wavelength | = | 3 x 107 / T |
| = | 3 x 107 / 3 | |
| = | 107 Angstroms ~ 0.1 cm |
which is in the microwave region of the spectrum. Thus, the 3 K background radiation is also called the cosmic microwave background.
2. By the Wien Law,
| Wavelength | = | 3 x 107 / T |
| = | 3 x 107 / 5800 | |
| = | 5172 Angstroms |
This is in the yellow-green portion of the visible spectrum.