LED at 60 HZ? (was RE: Radio Shack Strobes)

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Original poster: "Daniel Kline" <daniel_kline-at-med.unc.edu> 

An engineering friend says a high-brightness LED on a
low-voltage transformer, like 6 Volts, connected through
a suitable resistance, should flash at 60Hz in sync with
the 60Hz mains. (50Hz for you all over there :)
It seems too easy to me...he thinks that the LED may have
a "persistence" issue. In other words, just because it
turns off quickly doesn't mean it stops emitting quickly.
Comments?
Thanks,
Dan K