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Quantum Wonders card QTM-37, Lasers, with a glowing paper-cut illustration. It reads: A laser is light whose photons march in step: the same colour, heading the same way.

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Lasers

What’s going on

In 1917 Albert Einstein predicted stimulated emission: a passing photon can coax an excited atom to release a second photon that is its exact twin, with the same colour, direction and timing. A laser bounces light between mirrors so that twins make more twins, building a strong, tidy beam. Lasers read barcodes, carry internet data through glass fibres and help surgeons treat eyes.

Myth

Laser beams always glow like the streaks in films.

Fact

From the side, you see a beam only where dust, mist or air scatters some of it.

Learn more

Nobel Prize in Physics 1964 (masers and lasers), nobelprize.org.

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QTM-37 from Quantum Wonders, free quantum physics cards for ages 10 to adult

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