In 1945, Raytheon engineer Percy Spencer was standing near an active magnetron, a vacuum tube used in radar equipment, when he noticed something odd. What happened, and what did he do next that led to the microwave oven?
- A nearby lightbulb dimmed sharply and its filament began to hum whenever the magnetron powered on, which he then measured with an oscilloscope
- A chocolate bar in his pocket melted, so he began testing whether the magnetron's energy could cook other foods, starting with popcorn kernels and then an egg
- His wristwatch stopped working entirely, so he investigated whether the magnetron emitted a magnetic field strong enough to disrupt small mechanical devices
- The magnetron's metal casing became too hot to touch within seconds, so he began researching heat-resistant materials for a new casing design
Why B? And why not the others?
Correct answer: B. A chocolate bar in his pocket melted, so he began testing whether the magnetron's energy could cook other foods, starting with popcorn kernels and then an egg
The chocolate bar in Spencer's pocket melted while he stood near the working magnetron, and instead of dismissing it he tested the effect deliberately, first on popcorn kernels, which popped, and then on an egg, which burst; this convinced him the magnetron's energy could cook food, leading to Raytheon's first commercial microwave oven, the RadarRange, in 1947. The option describing a dimming, humming lightbulb is wrong because that describes an electrical interference symptom, not the food-related anecdote that actually pointed Spencer toward cooking. The option describing a stopped wristwatch is wrong for the same reason: a magnetic disruption of a mechanical device has nothing to do with heating food and is not the observation credited with the invention. The option describing an overheating outer casing is wrong because it would only prompt research into casing materials, not the insight that the radiation itself could cook something.
Source: Britannica-adjacent: Massachusetts Historical Society, "Percy Spencer, Inventor of Microwave Oven, Born"