Photons in a laser beam have the same energy, wavelength, polarization direction, and phase because?

Answer: each is produced in an emission that is stimulated by another
Explanation

Lasers operate on the principle of stimulated emission, proposed by Einstein.


In stimulated emission, an incoming photon stimulates an excited atom to drop to a lower energy level, releasing a new photon.

This new photon has:

  • Same energy
  • Same wavelength
  • Same polarization
  • Same phase and direction
  • as the photon that stimulated it.

Because of this process, all photons in a laser beam are coherent, monochromatic, and travel in the same direction — a unique property of laser light.

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