Does Light Have Mass? Weight of Photon Explained

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    Photon Weight
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Discussion Overview

The discussion revolves around the question of whether light has mass, specifically in the context of measuring the effects of light on a weighing machine in a vacuum chamber. Participants explore the implications of light's momentum and pressure in relation to mass.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant poses a question about whether focusing light on a weighing machine would cause deflection, suggesting this could imply light has mass.
  • Another participant clarifies the scenario by asking how the light is focused and notes that light can transfer momentum, which could affect the scale.
  • A subsequent reply confirms the scenario of light coming from above and focused on a sensitive scale, indicating that this setup could produce measurable effects.
  • It is mentioned that light has momentum and that this momentum can create pressure, which when multiplied by surface area results in a measurable force on the scale.
  • One participant expresses appreciation for the explanation and indicates a need for further review of the concepts discussed.
  • Another participant questions the relevance of mass in relation to photons, suggesting a disconnect between light's effects and the concept of mass.
  • A later reply asserts that a photon has no mass.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between light's effects on a scale and the concept of mass, with some asserting that light's momentum can be measured while others maintain that photons do not possess mass.

Contextual Notes

The discussion includes assumptions about the nature of light and its interaction with matter, as well as the definitions of mass and momentum. There are unresolved questions regarding the implications of light pressure and the conditions under which measurements would be taken.

Who May Find This Useful

This discussion may be of interest to those exploring the properties of light, momentum, and the conceptual understanding of mass in physics.

dev70
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hi pf, my friends asked me a strange question to me today,
"if in a vacuum chamber if light is somehow focused on a suitable weighing machine then will there be any deflection?
if yes does that mean light has mass? "

sounds strange, isnt? that why i choose to ask here?
 
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Focused in which way? Coming from above, reflecting light upwards? This will transfer momentum, and the scale will change.
Focused to have a high and constant energy density close to some (hypothetical) very sensitive scale? The scale should see an attraction.
Something else?
 
coming from above, and focused on a sensitive scale..
 
Light has a momentum, and momentum times intensity is a pressure. Pressure times surface area (of your scale, or focus) is a force, and the scale can measure this.
The Nichols radiometer is not a scale, but it operates with light pressure.
 
wow..beautiful explanation. i think i got it... i need some time for review..thanks by the way
 
i guess it doesn't have anything to do with mass of photon?
 
A photon has no mass.
 

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