Electromagnetic absorption by water
The absorption of electromagnetic radiation by water depends on the state of the water.
The absorption in the gas phase occurs in three regions of the spectrum. Rotational transitions are responsible for absorption in the microwave and far-infrared, vibrational transitions in the mid-infrared and near-infrared. Vibrational bands have rotational fine structure. Electronic transitions occur in the vacuum ultraviolet regions.
Its weak absorption in the visible spectrum results in the pale blue color of water.