Cutting slits in great big wheels might be a bit too "19th-century" for your liking. If so, you might prefer another way to achieve stroboscopic effects: using a rapidly flashing lamp called a strobe light. A strobe light works in an exactly equivalent way to a stroboscope. Imagine you're looking at a wagon wheel trundling down your street, only at midnight. It's pitch black so you can't really see the wheel, much less those pesky spinning spokes. Suppose you flick on your flashlight very briefly then flick it off again. The wagon wheel will light up. Now if you could flick your light on and off 24 times a second, and the wheel was rotating at the same speed as before, the spokes would flicker but appear stationary.
Photo: Strobe lights work in a similar way to the xenon flash lamps used in cameras, but are designed to fire faster and much more often.
Sounds good, doesn't it? Unfortunately, switching an ordinary light on and off this quickly is virtually impossible. Ordinary lamps work by a process called incandescence, where electricity flowing through a filament (thin coil of wire) generates heat and light at the same time. Incandescent lamps may appear to come on the minute you flick a switch, but it takes time for the filament to heat up and cool down, so they can't flash rapidly on and off. Fluorescent lamps take even longer to work, so they're no good either. What we need is a lamp that makes a bright, instant flash a bit like a mini bolt of lightning—something like the xenon flash lamp in a camera. Now in a camera, flash lamps often take many seconds to activate, because they're powered (through a capacitor) by low-voltage batteries. With a high-voltage power supply, rapid charging isn't a problem—and xenon lamps like this can be made to flash on and off dozens of times each second. (Note that you can also make a strobe flashlight by putting a stroboscope—a rotating disc with slits cut into it—in front of an ordinary incandescent lamp.)