File talk:Black body visible spectrum.gif
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Dear Dariusz Kowalczyk,
I was wondering about the rising intensity towards longer wavelength. So in your graph it looks like there is a minimum peak intensity is at ~550nm. In my oppinion the peak intensity should rise whith decreasing wavelength.Can you please prove that?
sincerly yours, sheevar
- Each graph building this animation was calculated from Planck Law (equation). There is no minimum in these charts. The intensity for low temperatures is rising, for high decreasing, the graph for average temperatures is almost flat in the range 380-780 nm, what makes impression of such minimum. Actually there is small maximum (not minimum) in the middle at ~550nm (for average temperatures). This chart makes only impression of such minimum because graphs in this animation are changing from higher on the left to higher on the right through almost flat curve. And these changes are lowest at ~550nm.
Original Planck graphs here are additionally changed proportionally to to keep equal areas between functions and horizontal axis (they are flattened or stretched, Bλ scales are different for each one and Bλ values can't be compared between temperatures). This was made because original graphs differ very much in size (Bλ values) and they would be difficult to compare on one image. And because this animation is aimed to show differences in relative intensities between low and high wavenlengths, not their absolute values. These graphs show simply that there is more red than blue for low temperatures, more blue than red for high temperatures and equal amounts of blue and red for average temperatures. But this transformation doesn't change answer to your question.
And look here:
The maximum at ~550nm is visible for about 5000 K, for low (~3000 K) and high (something like ~8000K, not shown in the above image) temperatures there is no maximum in the visible range. By the way - note how much these graphs differ in hight. 8000K is far to high to show here. This is why they are streched or flattened in the discussed image. They could be shown eventually in one image in logaritmic scale too (log(Bλ) instead of Bλ) ... But they would be distorted too much perhaps.
Darekk2 (talk) 13:56, 28 May 2015 (UTC)
- Each graph building this animation was calculated from Planck Law (equation). There is no minimum in these charts. The intensity for low temperatures is rising, for high decreasing, the graph for average temperatures is almost flat in the range 380-780 nm, what makes impression of such minimum. Actually there is small maximum (not minimum) in the middle at ~550nm (for average temperatures). This chart makes only impression of such minimum because graphs in this animation are changing from higher on the left to higher on the right through almost flat curve. And these changes are lowest at ~550nm.
I woud like to stop this animation - or better: to move it by a slider from 1000 to 20000K (right now it is too fast for my eyes). --12:04, 14 February 2018 (UTC)
Love this graphic. I only wish it were about 1/4 of the frame rate so that I could read the temperature at the right time. (4k maybe?) -- 207.140.43.82 17:41, 23 April 2018 (UTC)
