Point 6 of 27 — Lesson 1: Laser Physics, Population Inversion and the Helium-Neon LaserQuestion bank: 1 questions (1 with pictures)
06Collimation (a parallel narrow beam)
In an ordinary source the beam widens as it moves away; the energy spreads over a larger and larger area.
The diameter of a laser beam remains almost constant for long distances, because all photons move in the same direction.
A laser beam can therefore carry energy over long distances without much loss.
For example, a laser beam sent to a reflector placed on the Moon's surface (about 380 000 km away) returns to the Earth, and the time of the round trip gives the distance accurately.
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