Radiant Heat Energy: Why is Hand Protected Behind Glass?

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Discussion Overview

The discussion revolves around the phenomenon of radiant heat energy and the effects of glass as a barrier. Participants explore why a hand does not feel radiant heat from a fireplace when placed behind glass, while also questioning the relationship to the greenhouse effect. The scope includes conceptual understanding and technical reasoning related to thermal radiation and transparency of materials.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions why their hand does not feel radiant heat from a fireplace behind glass, despite being able to see the fire.
  • Another participant introduces the greenhouse effect, suggesting a possible connection to the discussion.
  • A different participant expresses doubt about the initial observation and asks why their hand can feel radiant heat from the sun when placed under glass.
  • There is a mention of barriers that are opaque to infrared radiation but transparent to visible light, indicating that such barriers allow energy in while blocking heat loss, highlighting the differences in radiation spectra.

Areas of Agreement / Disagreement

Participants express differing observations and interpretations regarding the effects of glass on radiant heat, indicating that multiple competing views remain without consensus on the explanations provided.

Contextual Notes

The discussion includes assumptions about the properties of glass and its interaction with different wavelengths of radiation, which may not be fully articulated or agreed upon by all participants.

westdivo
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why does your hand not feel the radiant heat energy from a fireplace if you place it behind a sheet of glass, even though you can see the fire very easily?
 
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I've never noticed that. Do you know the greenhouse effect?
 
Really? I doubt it.
Why can my hand feel the radiant heat from the sun if we place it under glass?

And what is the relation between the question and the greenhouse effect?
 
zlbeidou said:
what is the relation between the question and the greenhouse effect?

If you have a barrier (glass or atmosphere) that is opaque to infrared but transparent to visible light, it will let plenty of energy in during the day, and still block much of the heat-loss during the night. (The key is the differences between the radiation spectra from either side.)
 
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