Does your office lighting make you feel weary and dreary?  The cure may be at hand!  Recently, Professor Derk-Jan Dijk of the Surrey Sleep Centre has led a team testing out new bulbs with a colour temperature of 17,000 Kelvin and found that they increase alertness as compared with more traditional types of lighting. But this sounds rather alarming.  17,000 Kelvin would be the temperature of a star close to B3 in the main sequence, somewhere between Alkaid and Regulus in properties.  The luminance of these stars is largely in the ultraviolet, and they would give one a lethal suntan in about a minute. 

However, maybe I am panicking too soon.  I remember on a visit to Hong Kong about 20 years ago and they (as usual about 10 years ahead of Britain with the technology) were already very much into low-energy light bulbs.  Looking at the blocks of flats at night, the windows of those that were still using tungsten shone yellow, whereas those with low-energy bulbs appeared slightly bluish.  My friend had low-energy light bulbs, and also some violet glasses which he had brought back from Venice.  Mirabile dictu (I might as well throw in a bit of Latin because in Britain we may soon not be allowed to, see “Councils ban ‘elitist’ and ‘discriminatory’ Latin phrases”) they were shining indigo. 

Was this something weird about the spectrum of these bulbs, or were the glasses themselves fluorescing in some ultraviolet that might have been sneaking out of the low energy bulbs?

Any misgivings about the latter are put to rest by looking at Spectra from HNU Photonics in Hawaii.  They produce LED lighting, and their website hosts comparison spectra of LEDs and Tungsten, and of LEDs and fluorescent lamps.  The latter show a strong spectral spike in the indigo, which would really put the Venetian glass into “Mood Indigo”.  (But sorry to point out, Hank,that while surprisingly the Tungsten Halogen lamps are strongest in the violet,the LEDs don’t “do” violet at all!) 

You can see more spectra of fluorescent lamps in Spectra around us - studies with a home-made spectroscope from EU-HOU. 

Referring to the published article (like we like to do on Scientific Blogging) I found that these 17,000 Kelvin lamps are a newly developed type of fluorescent from Philips called “blue-enriched”.  As their spectra (below with comparison solar spectrum) show, they have a massively increased hump in the blue-violet end of the spectrum (arrowed), where the “baseline” typical office fluorescent only has the spike of the mercury spectral line.   Nothing at all like the black body rising into the ultraviolet version that one would get from a sizzling B3 star!   And the study shows that they do help keep one awake! 

Would such a background, one asks, help to prevent “Death by PowerPoint”?

Sources: University of Surrey Press Release:Office workers given the blue light to help alertness

Original article and source of lamp spectra:   Scandinavian Journal of Work, Environment&Health 2008;34(4):297–306

Comparison solar spectrum: EU-HOU.