How Does the Gradient Force Arise in Lasers?

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Discussion Overview

The discussion revolves around the nature of the gradient force in lasers, specifically addressing how particles experience electrical forces in the presence of laser light. It explores concepts related to electromagnetic waves, radiation pressure, and the behavior of particles within a laser beam.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions the existence of an electrical gradient in lasers, noting that lasers consist of monochromatic photons and inquiring how a particle could feel an electrical force.
  • Another participant explains that lasers emit coherent electromagnetic waves, which consist of alternating electric and magnetic fields, and states that higher intensity results in greater forces on particles in the beam path.
  • A different participant mentions that in a polystyrene bead placed in a laser, only the refracted wave contributes to the electrical gradient, questioning the role of the reflected wave.
  • A repeated inquiry emphasizes that the electrical gradient arises due to the spatial variation in intensity of the laser light.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms behind the electrical gradient in lasers, with some focusing on the role of electromagnetic waves and intensity, while others raise specific questions about the contributions of refracted versus reflected waves. The discussion remains unresolved regarding the precise nature of the electrical gradient.

Contextual Notes

There are limitations in the assumptions made about the behavior of particles in laser light, particularly regarding the definitions of electrical gradients and the effects of different types of waves (reflected vs. refracted).

rida
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how come there is an electrical gradient in lasers? i means lasers are just monochromatic photons so how come a particle feels an electrical force there
 
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A laser emits coherent electromagnetic waves. That's what light is; an electromagnetic wave. This wave consists of electric and magnetic fields that constantly alternate from + to - and back. The higher the intensity of the light, the greater the electric and magnetic forces felt by a particle in the beam path.

Also, depending on the size of the particle and the wavelength, the particle can experience radiation pressure by absorbing or reflecting light, taking some of the lights momentum and being accelerated away from the source.
 
in polystyrene bead placed in lase, only the refracted wave is responsible for electrical gradient not the reflected one. how come it is so
 
rida said:
how come there is an electrical gradient in lasers? i means lasers are just monochromatic photons so how come a particle feels an electrical force there

Because the intensity varies in spatial extent.
 

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