Hi all, I have a few questions in regards to UV light (or any other light on the spectrum) and if any one could point me in the direction of any textbook or online resource to read up it would be appreciated. I would like to know how you can figure out the amount of energy required to produce UV light so that it can penetrate a certain distance, for example: I want to emit a 'beam' of UV light over a length of 2 metres, how can this be figured out? and is there any way to find out how much of the UV lights 'concentration' has been dissipated into the surrounding atmosphere. Sorry, I do not have the strongest suit in this type of physics. Thank you!