Lasers

Definition

A device that produces an intense, narrow beam of light in which the waves are of a single colour and march in step; the word stands for Light Amplification by Stimulated Emission of Radiation.

Key points

• Laser light is monochromatic (single wavelength), coherent (waves in phase), and highly directional (it spreads very little), unlike ordinary light from a bulb.
• It is produced by exciting atoms so that they release identical photons in a chain, amplified between mirrors in a cavity.
• Everyday and industrial uses include barcode scanners, optical disc readers, laser printers, fibre-optic communication, cutting and welding metals, and measuring distance.
• Medical uses include eye surgery (such as LASIK) and removing tissue precisely; surveying and the measurement of the Earth-Moon distance also rely on lasers.
• Defence uses include range-finding, target designation, guidance, and developing directed-energy weapons.

Why it matters for CAPF

The meaning of LASER, the properties of laser light (monochromatic, coherent, directional), and its uses in communication, medicine, and defence are common physics and technology facts.

Common confusion

Laser light differs from ordinary light mainly in being coherent and single-wavelength, not simply in being brighter. A laser is a source of light; it is not itself part of the electromagnetic spectrum, though the light it emits falls within that spectrum.

Related concepts

concept electromagnetic spectrum, concept optical fibre, concept total internal reflection

Parent note

physics everyday