Analyze the absorption spectrum for water: What type of EM radiations are mostly
ID: 891207 • Letter: A
Question
Analyze the absorption spectrum for water: What type of EM radiations are mostly absorbed by water molecules? What types of radiations go through this liquid without much being absorbed? How would you explain that the spectrum shows such wide absorption bands? How would you use the data to explain why water is a clear liquid with a bluish tint? How would our ability to do observations of celestial objects be affected if water were to strongly absorb EM radiation at all wavelengths? How might the nature of the EM radiation absorbed and not absorbed by water have influenced the evolution of organs to detect light (e.g., eyes) in living organisms?Explanation / Answer
From the spectrum we see, Water absorbs mostly in UV-VIS region, approximately between 2x102 --9x102 nm wavelength. Rest of the UV region and the whole IR region go through this liquid without much being absorbed. Absorption bands are wide because water molecules, due to H-bonding forms many closely spaces energy levels, the transitions superimpose and gives rise to wide bands. From the spectrum we see water absorps most in the Near UV and in the shorter wavelengh side of Visible region i.e., in the 'VIB' part of VIBGYOR . TO naked eye UV is colorless, so this explains why water is a clear liquid with a bluish tint. We observe celestial bodies by detectings the radiations (like gamma-rays) falling on earth from them. If water absopbed all EM radiations of all wavelengths strongly, we would not be able to detect any radiations from them as the water vapour in the atmossphere would have already absorbed those radiations. Since water doesn't absorb much in the Visible region, our eye has a layer of water in front of it, so that visible light can easily pass through and fall on the retina so that we can 'see' all colours.