Light, wavelength and optical filters

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Discussion Overview

The discussion revolves around the relationship between the color of light, its wavelength, and the use of optical filters in the context of coral propagation. Participants explore how different wavelengths affect coral growth and whether standard light sources can be modified with filters to achieve the desired light spectrum for corals.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the relationship between the color of light emitted by bulbs and their corresponding wavelengths, particularly in relation to coral needs.
  • Another participant clarifies that while color corresponds to wavelength for monochromatic light, this relationship is more complex when multiple wavelengths are present.
  • There is a discussion about the potential of using optical filters to limit or filter light from standard bulbs to meet the specific wavelength requirements for coral growth.
  • One participant suggests that using standard daylight bulbs with optical filters could be a cost-effective solution for providing the necessary light for corals.
  • Concerns are raised about whether the filters would effectively provide the desired wavelengths and whether additional light at different wavelengths could be harmful.
  • Another participant mentions the difficulty in obtaining spectral data for commercially available bulbs, which complicates the decision-making process regarding their use with filters.
  • There is a mention of the potential for algae growth on different parts of the spectrum, suggesting that filters might be beneficial in preventing unwanted algae growth while supporting coral health.

Areas of Agreement / Disagreement

Participants express varying views on the effectiveness of using optical filters with standard bulbs for coral growth. While some see potential in this approach, others raise concerns about the complexity of light spectra and the need for specific wavelengths. The discussion remains unresolved regarding the best methods and implications of using filters.

Contextual Notes

Participants note limitations in accessing spectral data for light sources, which may affect their understanding and decisions regarding the use of optical filters. There is also uncertainty about the effects of additional wavelengths on coral health.

Jeprox
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Hi, I have read from previous topic regarding color of light vs wavelength. It is a bit confusing for on my self as I do not have any background on this. Hopefully someone could chime in and educate myself. Here it goes,

it has been lingering in my head that the color of light emitted by a bulb (or any other source) corresponds to the wavelength. I am into corals and they need a specific light wavelength/ color (if I may say) which is around 430nm to 500nm to thrive base on my readings on coral propagation. Most light sources (fluorescent, LED) have purplish or bluish shade if we go for that range of wavelength. An example, actinitic light bulbs are on this color and fall within the wavelength range (430 to 485nm). Am I correct to say that my assumption or notion on color vs wavelength is correct?

Another thing, I have read that using optical filters (glass or plastic sheets) could limit/filter the light on the discharge side. Say, I buy a PAR 38 LED bulb (daylight) then use an optical filter (plastic sheet or glass) to emit color or wavelength necessary for coral growth (which is stated above). Can I do this?

I am trying to make my hobby more economical by enlightening myself (and others) using scientific facts. If the above is doable, this is great news.

Please help.

Thanks.
 
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Jeprox said:
it has been lingering in my head that the color of light emitted by a bulb (or any other source) corresponds to the wavelength.
This is a good concept for monochromatic light, it doesn't work if you have multiple wavelengths in the light. The color your eye and brain visualize then depends on details of the human eye and brain. Something the corals don't care about.
Jeprox said:
Another thing, I have read that using optical filters (glass or plastic sheets) could limit/filter the light on the discharge side. Say, I buy a PAR 38 LED bulb (daylight) then use an optical filter (plastic sheet or glass) to emit color or wavelength necessary for coral growth (which is stated above). Can I do this?
The filter will remove some wavelength (range), it won't add light that was not present before. Check the emission spectrum of your available light sources to see if they have the right range in them.
 
Hi mfb, thanks for your reply.

For corals, different acropora species require different wavelength. This is being reflected on the coloration intensity that they show when subjected to correct light.

The monochromatic type of light for corals are very costly, especially the led lights. This is the reason why I am trying to decipher the relationship of color vs wavelength and optical filters. If my guess is correct, it is cost effective and cost efficient to buy standard daylight bulbs paired with a highly efficient optical filter to deliver filtered light with specific wavelength range.

With regards to optical filters: my bulb is rated as daylight and white in color. As per my readings, it would take a mixture of colors to create white. I only need the blue and indigo colors (430 to 486nm) which is present in white light. Correct to say that i could use optical filters to have light emission of this range for white light?

i could not check the emission of light spectrum of commercially available, big box store type flourescent, cfl and led bulbs as they are not published and also not shown in the manufacturers website

Sorry if i have confused you. I am just trying to educate myself.
Thanks again for your help.
 
Jeprox said:
With regards to optical filters: my bulb is rated as daylight and white in color. As per my readings, it would take a mixture of colors to create white. I only need the blue and indigo colors (430 to 486nm) which is present in white light. Correct to say that i could use optical filters to have light emission of this range for white light?
It is possible to get light that appears white without that wavelength range. Without the spectral data or details about the light production process you can't be sure.
Blue LEDs shouldn't be that expensive. Their power consumption is significantly lower as well.

I'm not sure if you need the filters at all: is additional light at different wavelengths harmful?
 
Sir, thanks again for your reply.

If I may explain, what I am trying to do is try to find out the el cheapo way of coral keeping. Lighting is one of the major expense of the hobby that has many myths.

base on the experimentation done by one enthusiast, corals will thrive on the previously mentioned wavelength. Algae, on the other hand will grow on the yellow and red side of the color spectrum. And we don't want that.

If I can use a regular cfl bulb and just add a filter to sustain coral growth, that would be nice. Then I can spread the word on it.
 
See some example spectra. There is probably some intensity in the right wavelength range.

Okay, if algae grow using different wavelengths then filters sound useful.
 
Thank you.
 

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