What determines the colour? Frequency or wavelenght?

Click For Summary

Discussion Overview

The discussion centers around the question of what determines the color of light, specifically whether it is frequency or wavelength that plays the primary role. The scope includes theoretical considerations and explanations related to the electromagnetic spectrum and the perception of color.

Discussion Character

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

Main Points Raised

  • Some participants note that high frequencies correspond to small wavelengths, leading to blue-shifted colors, while low frequencies correspond to red colors, referencing the electromagnetic Doppler effect.
  • It is mentioned that frequency and wavelength are inversely related, as their product equals the speed of light, suggesting that either can be used to describe color.
  • One participant argues that the wavelength of light also depends on the medium through which it passes, asserting that the frequency is what determines the color perceived.
  • Another point raised is that the energy of photons received by retinal cells determines color, with equations provided to relate energy to frequency and wavelength in the context of the eye's fluid.
  • A later reply emphasizes that while the energy of a photon depends on its frequency, this frequency remains unchanged when light transitions between different media.

Areas of Agreement / Disagreement

Participants express differing views on whether frequency or wavelength is more fundamental in determining color, with some asserting the primacy of frequency while others highlight the role of wavelength and medium. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Some claims depend on specific definitions of color and the context of light propagation, including the effects of different media on wavelength. There are unresolved aspects regarding the implications of the Doppler effect and the relationship between energy, frequency, and wavelength.

darkar
Messages
187
Reaction score
0
What determines the colour? Frequency or wavelength?
 
Physics news on Phys.org
darkar said:
What determines the colour? Frequency or wavelength?


Normally high frequencies correspond to small wavelengths, and this correspond to colours that are blue-shifted. In the EM-spectrum blue is high energy, and red is low energy. these colors come from the EM-variant of the Doppler-effect. An EM-spectrum can be "made" when reflected sunlight from a planet undergoed emission or absorption processes when passing through our atmosphere. So we will see lines that move to blue when a planet is moving towards us. lines will be moved to red when the planet moves away from us. This is the EM-Dopplereffect.
 
Frequency times wavelength is the speed of light, so they are inversely related and either of them can be used.
 
selfAdjoint said:
Frequency times wavelength is the speed of light, so they are inversely related and either of them can be used.

That's not a complete answer: the wavelength depends also on the medium through which the light passes. The color we see is determined by the frequency.
 
It depends on the energy of the photons our retina cells receive. This energy would be E = hf or E = hv/\lambda_{eye fluid}, with h plank's constant, and v = c/n_{eye fluid} is the speed of light through the fluid in our eye.
 
Just a note: The energy of a photon depends on its frequency, which does not change when light passes from one medium to another.
 

Similar threads

Colour depends on wavelength or frequency?
  • · Replies 22 ·
Replies
22
Views
1K
High School What's the reason microwave oven frequencies are at 2.45 Ghz?
  • · Replies 30 ·
2
Replies
30
Views
14K
High School Sun's peak wavelengths and chlorophyll's green colour
  • · Replies 27 ·
Replies
27
Views
3K
High School Multiple frequency EMFs and capacitors
  • · Replies 9 ·
Replies
9
Views
1K
Undergrad Magnetic Component Permeability vs Frequency Loss
  • · Replies 21 ·
Replies
21
Views
2K
Undergrad Is colour dependent on wavelength of frequency?
  • · Replies 19 ·
Replies
19
Views
12K
High School Single phase induction motor Torque under increased frequency and Same Current
  • · Replies 4 ·
Replies
4
Views
2K
High School Can you read my English on 4 colour theorem?
  • · Replies 8 ·
Replies
8
Views
2K
Undergrad Best frequency of radio light to penetrate 1 meter of sea water?
  • · Replies 29 ·
Replies
29
Views
3K
MS 365 Profile Badge colour
  • · Replies 5 ·
Replies
5
Views
839