Light

[E. & O. E.]

Hi Sanjay,

much thanks for your great articles about light! I read them with pleasure.
You wrote, "...that photons are generated when electrons shift from a higher energy level to a lower level and these energy levels are discret." That´s right. But looking at figures 2,3, etc (of part II, photons) I see a continuous distrubution of wavelenghts. Doesn´t that mean, that a HQI-bulb emitts (sends out) all possible wavelengths between 400 and 700 nm?! But that´s an infinite number! So my question: Why are there no "black holes" in the distribution? Or in other words: Why is there a continuous spectrum instead of an expected line spectrum?
And by the way: In your figures sunlight is shown as a contiuous spectrum. But remember the Fraunhofer-lines - there are a lot of wavelenghts missing in the sunlight! Do you know, whether anybody ever checked out, whether the wavelengths corresponding to the Fraunhofer-lines are missing in the light from our HQI-bulbs, too? Otherwise we illuminate our corals with wavelengths, which they have never seen in their life ... Please excuse my bad English With kind regards, Erwin

[Sanjay]

Erwin:

The appearance of the spectrum depends on the measurement resolution and presentation. I do not think the spectroradiometers we trypically use can catch the Fraunhofer-lines. For most practical applications this is fine since most organisims have a very broad absorption spectrum. The data presented is taken at 2 nm intervals and as plotted it tends to appear smooth and continous.

The metal halides also have a very "spikey" output corresponding to the halide and mercury vapor mix and in reality it would be a lot of lines distributed throughout the wavelength range. Its quite likely that there may be similar Fraunhofer lines for MH but I have not seen them reported anywhere, or thier impact on corals.

Hope this answers your questions.

sanjay.