Why do darker colors absorb heat/light?

  • Thread starter Thread starter RuroumiKenshin
  • Start date Start date
Click For Summary

Discussion Overview

The discussion centers around the question of why darker colors absorb heat and light, exploring the relationship between color, light absorption, and energy. Participants delve into the mechanics of color perception, the behavior of light with different materials, and the implications for energy absorption.

Discussion Character

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

Main Points Raised

  • Some participants suggest that color is determined by the wavelengths of light that are absorbed and reflected, indicating that the question may be self-answering.
  • There is a proposal that colors correspond to specific wavelengths of light, with darker colors absorbing more wavelengths that are not reflected.
  • One participant mentions a "reverse radiometer" as an example of how different colors can absorb sunlight differently, leading to kinetic energy generation.
  • Another participant questions the efficiency of radiometers in converting light to motion, suggesting that the heating of gases within the device is a more significant factor than photon momentum transfer.
  • A participant raises a question about why leaves absorb all colors except green, indicating a curiosity about the mechanisms of photosynthesis and light absorption.
  • There is a correction regarding the specifics of chlorophyll absorption, with a focus on the wavelengths involved in the photosynthetic process, although this correction does not resolve the broader question of color and heat absorption.

Areas of Agreement / Disagreement

Participants express various viewpoints on the relationship between color, light absorption, and energy, with no clear consensus reached on the mechanisms involved or the implications of these relationships.

Contextual Notes

Some claims about the efficiency of energy conversion in radiometers and the specifics of chlorophyll absorption are made, but these remain unresolved and depend on further clarification of underlying principles.

RuroumiKenshin
Why do darker colors absorb heat/light?
 
Last edited by a moderator:
Biology news on Phys.org


Originally posted by MajinVegeta
Why do darker colors absorb heat/light?

The question needs minor re-phrasing. You see, the fact that something is a certain color is caused by it's absorbing certain wave-lengths of light (not the other way around).
 
The question needs minor re-phrasing. You see, the fact that something is a certain color is caused by it's absorbing certain wave-lengths of light (not the other way around).
More minor clarification: The color is caused by BOTH what is absorbed and what is reflected (for opaque objects).

So the question is self-answering.
 
Now that the question has been re-phrased, perhaps someone would like to answer it?

Oh, OK...i'll do it...

What they mean Majin, is that our experience of colour occurs because only particular light wavelengths of the spectrum are reflected. The wavelengths which are reflected are what we see, and the wavelengths which are absorbed are the colours we do not see.

So a green leaf, is actually absorbing all of the colours which are not green (to oversimplify...)

As for colours absorbing heat. I ahve never heard that as such. Colours = Light though, and light = energy, and energy = heat... maybe there is some sort of connection there.
 
Originally posted by Another God
Now that the question has been re-phrased, perhaps someone would like to answer it?

Oh, OK...i'll do it...

What they mean Majin, is that our experience of colour occurs because only particular light wavelengths of the spectrum are reflected. The wavelengths which are reflected are what we see, and the wavelengths which are absorbed are the colours we do not see.

So a green leaf, is actually absorbing all of the colours which are not green (to oversimplify...)

As for colours absorbing heat. I ahve never heard that as such. Colours = Light though, and light = energy, and energy = heat... maybe there is some sort of connection there.

Have you ever seen a "reverse radiometer"? (At least I think that's what it's called.) I saw it on the deleted scene of "The Time Machine". It looked a lot like a wind-mill, but moved by the energy of the sun, as opposed to the energy of wind. You see, it's fins were colored white on one side, and black on the other side, and thus only one side of each fin was absorbing the sun-light, while the other side reflected it. This translated to kinetic energy, and the "reverse radiometer" began to spin.
 
As for colours absorbing heat. I ahve never heard that as such. Colours = Light though, and light = energy, and energy = heat... maybe there is some sort of connection there.
Yeah, the connection is the one you made. By the commutative property of math, light = heat (more or less). Every color corresponds to a specific temperature.
I saw it on the deleted scene of "The Time Machine".
You mean you DIDN'T have one in your high school physics lab? Wtf?!
 
If you hold up a vial of chlorophyl dissolved in alcohol, its reflected light (light behind you) appears green, but its transmitted light (light behind vial) appears red! The differences between frequencies times Planck's constant must be close to the reaction energy of ATP<-->ADP?
 
Most radiometers are not sensitive enough to turn primarily by photon momentum transfer. Rather, the black and white sides of the fins heat up differentially the rarified gas present within the radiometer and cause motion with the white side leading. Photons, I think, would cause rotation in the opposite direction. Not an efficient way to generate large amounts of energy here on Earth.
 
ermz ..so why do leaves absord all the other colours except for green?
 
  • #10
Originally posted by Loren Booda
If you hold up a vial of chlorophyl dissolved in alcohol, its reflected light (light behind you) appears green, but its transmitted light (light behind vial) appears red! The differences between frequencies times Planck's constant must be close to the reaction energy of ATP<-->ADP?

Actually, that's not correct. The reaction centers in chloroplasts absorb two photons, at 680 and 720 nanometers. This is used to reduce water, shunt protons across a membrane, and reduce NADP+. The protons go on to produce ATP, and the NADPH drives the Kreb's cycle, which produces sugars, which can be oxidized to produce ATP. But it's a far, far way from being a 100% effecient system.
 

Similar threads

How Does Flickering Light Influence Our Brain's Perception of Image Brightness?
  • · Replies 8 ·
Replies
8
Views
6K
Chornobyl Dark coloured tree frogs
  • · Replies 3 ·
Replies
3
Views
4K
Why does my beard look darker when longer?
  • · Replies 2 ·
Replies
2
Views
1K
Why doesn't blood dry inside our bodies?
  • · Replies 8 ·
Replies
8
Views
6K
Undergrad Question about the absorption of heat based on color
  • · Replies 4 ·
Replies
4
Views
4K
Why Does DNA Absorb Best at 260nm in Molecular Biology?
  • · Replies 1 ·
Replies
1
Views
3K
High School Question: What happens to absorbed light?
  • · Replies 16 ·
Replies
16
Views
24K
Undergrad How does the electron come back down in energy level after absorbing a photon?
  • · Replies 37 ·
2
Replies
37
Views
8K
What does it mean that when light is reflected the "wavelengths of each contributing hue are subtracted"?
  • · Replies 16 ·
Replies
16
Views
2K
Does nature choose aesthetic colors?
  • · Replies 2 ·
Replies
2
Views
2K