Published in Physics World, 18 May 2009
Here’s a little test: if an electron beam were coming towards you with an energy of 1 GeV, how much lead would you need to stop it?
It’s not an easy question to answer. Even if you knew the formula that links the kinetic energy of electrons to their stopping distance in lead, you would have to do a little maths before you found the correct result. But now there might be an easier way: go to Wolfram Alpha, an internet “computational knowledge engine” that officially launches today. […]
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