No single load will see240V. But with two loads in series the voltage in the lower wattage load approaches arbitrarily close to 240V as the impedance ratio increases. If the only loads are two 100 W incandescent bulbs, neither would light if only one was turned on.
When you turn in the second, on the opposite "phase", they might both light fine if their thermal characteristics match closely enough. But if one heats faster it could well hog the voltage drop and burn out. Then both would be dark again.
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