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<p>[QUOTE=&quot;-jeffB, post: 1350801, member: 27832&quot;]I&#039;ll pile in on this one, as a sometime laser (and general light-source) enthusiast.</p><p><br /></p><p>Coins tend to be reflective, which means that most of the light that hits them bounces off. They also conduct heat really well, so even if you focus the light down to a pinpoint (which is what lets lasers pop balloons and light matches), the heat will just disperse throughout the coin.</p><p><br /></p><p>So, unless you&#039;ve got a serious metalworking laser, nothing will happen to your coin. Even an illegal 50mW laser &quot;pointer&quot;, which can instantly produce blind spots in your eye, won&#039;t do a thing. The ludicrous 1W handheld lasers that are now becoming available would make the coin warm, but that&#039;s about it. Meanwhile, though, most of that power would be reflecting off the coin, and reflections at those power levels can burn a permanent blind spot into your retina before you can blink.</p><p><br /></p><p>I have a big (16x20-inch) Fresnel lens that I can use to focus sunlight onto a spot about the size of a cent. By my calculation, it dumps about 100 watts of power into that spot.</p><p><br /></p><p>If I put a clad dime or quarter at the focus, it gets really hot, and turns grey from oxidation.</p><p><br /></p><p>If I put a copper cent at the focus, it gets even hotter, and turns black from oxidation.</p><p><br /></p><p>If I put a zinc cent at the focus, the zinc melts, and escapes from the copper shell. If it&#039;s a very sunny day near the peak of summer, the zinc BOILS out of the shell, making wisps of zinc-oxide ash as it combines with oxygen in the air.</p><p><br /></p><p>I haven&#039;t tried it with a silver coin. If the coin was toned black, it&#039;s <i>possible</i> that it would melt, but unlikely.</p><p><br /></p><p>If you had a 10-watt laser that you could focus down to a tiny (&lt;1mm) spot, you might be able to burn or melt a hole through a coin. But I doubt you&#039;ll ever have a 10-watt handheld laser. And if you do get your hands on one, unless you&#039;re extremely careful and extremely lucky, it&#039;s probably the last thing you&#039;ll ever see.[/QUOTE]</p><p><br /></p>

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