Does visible light contain energy?

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Discussion Overview

The discussion centers around the nature of energy in visible light and its interaction with objects, particularly focusing on absorption, reflection, and the implications for the conservation of energy. Participants explore concepts related to the behavior of light in different spectra, including visible and infrared light, and how these interactions affect temperature and energy transfer.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that visible light behaves differently from infrared light, suggesting that colors seen are those reflected rather than absorbed, raising questions about energy conservation.
  • Others argue that absorbed energy in objects, such as a black object in sunlight, results in increased temperature, indicating that energy is not lost but transformed.
  • A participant mentions that the energy in light and infrared is fundamentally the same, noting that objects can reach equilibrium temperature where absorption equals emission.
  • Another point raised is that various systems, such as plants and solar panels, convert light energy into other forms, indicating multiple pathways for energy utilization.
  • Concerns are expressed about the long-term absorption of solar energy by Earth and its implications for energy conservation over billions of years.

Areas of Agreement / Disagreement

Participants express differing views on the nature of energy in visible light versus infrared light, with some asserting a difference while others maintain that they are fundamentally similar. The discussion remains unresolved regarding the implications of these interactions for energy conservation.

Contextual Notes

Participants do not fully address the assumptions underlying their claims about energy absorption and emission, nor do they resolve the complexities of energy transfer in different contexts.

Who May Find This Useful

This discussion may be of interest to those exploring concepts in physics related to light, energy transfer, and thermodynamics, as well as individuals curious about the practical applications of these principles in technology and nature.

tinkeringone
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I read that Infra red waves that are absorbed are emitted by objects. And that makes sense.

But then I read that it apparently works differently in the visible light spectrum, i.e. the visible light colors we see are only those that that aren’t absorbed, i.e. they’re only the ones that are reflected off the surface of an object. So if red, orange, yellow, green, blue, indigo, and violet color waves reach an object that’s painted red, the red is reflected off the object, and all the other colors are absorbed.
Wouldn’t that violate the laws of conservation? Isn’t that energy? If it’s energy, how could it keep going in there and never come back out?
 
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tinkeringone said:
Wouldn’t that violate the laws of conservation? Isn’t that energy? If it’s energy, how could it keep going in there and never come back out?

Leave a black object out in bright sunlight for a few hours... Then touch it. It will be hot. That's where the energy it absorbed has gone.
 
There is nothing different about the energy in light and the energy in IR. If you expose an object to the concentrated (optical) rays of the Sun for a while, its temperature may get so high that it starts to get red / white hot. It is radiating light energy, having absorbed light energy.
The actual wavelength of the radiated EM, depends upon the temperature.

Given long enough, an object will reach equilibrium temperature with its surroundings - when the rate of energy absorption equals the rate of emission. If you took an object and placed it in a perfectly reflecting sphere, along with a filament lamp, that object would end up glowing at the same temperature as the filament. This model is a bit flawed, the way it's stated because the filament temperature would rise uncontrollably without some control of the power supply because no energy would escape from the sphere, but it makes my point.
 
What sophiecentaur said.

Plants convert some of the energy into chemical energy.
Solar panels convert it to electricity.
Most objects just heat up a bit and re-radaite the energy in the infrared part of the spectrum.

PS: Have a think about planet earth. It absorbs quite a lot of light energy from the sun and has done so for billions of years. Where has the energy gone?
 

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