# Why is water transparent?

Some substances like copper sulfate for example have vivid colors. But why is water transparent? Does it not emit any visual light from the electromagnetic spectrum?

• A portion of the explanation can be found at this site. – Nicolau Saker Neto Dec 3 '14 at 21:41
• @NicolauSakerNeto So it is because of the reflection of the light and the interactions between the photons with light. But however, I thought water was transparent. Take tap water for example. Why transparent? I understand why it is blue (because of reflections and adsorptions) but how & why is transparent? – Asker123 Dec 3 '14 at 21:45
• did you mean "colorless"? – mykhal Oct 30 '18 at 12:25

Water is not, in fact, colourless, but is slightly blue. As you can see below, in the visible range, there is slightly more absorption toward the long wavelengths, so more blue light makes it through than redder light. However, the absorption is very low in the visible range so the blue colour is faint and not apparent unless looking through a significant thickness of water. The reason things like $\ce{Cu^2+}$ solutions appear so vividly blue is because they also absorb red light, but very strongly, so a good deal more blue light than red passes through the solution. (see here)