MadSci Network: Physics

Re: How can I measure the wavelength of light outside at night?

Date: Wed Apr 20 11:00:19 2005
Posted By: Kenneth Beck, Senior Research Scientist, Chemistry and Physics of Complex Systems, Pacific Northwest National Laboratory
Area of science: Physics
ID: 1112110057.Ph

Dear Alex,

I’m an astronomer/chemical physicist by training and solid state 
physicist by vocation. Until receiving your question, I really hadn’t 
thought much about ambient light effects on birds.  Then, I started 
reading about nocturnal lighting on the avian environments.  Fine sources 
of direct research can be found at these websites…


As these websites point out structural hazards are actually responsible 
for more bird kills than higher profile catastrophes such as oil spills.

In the dark, and especially in foggy or rainy weather, the combination of 
glass and light becomes deadly. Confused by artificial lights, blinded by 
weather, and unable to see glass, birds by the hundreds and even 
thousands can be injured or killed in one night at one building. 

“Over 140 different species of birds have collided with buildings in 
Toronto alone.”  It’s estimated that… “across North America, up to 100 
million birds die in nocturnal collisions each year.” Wow!

So, I think finding out more about the typical ambient lighting 
conditions for singing birds is an extremely worthwhile endeavor.  There 
are a couple of way to do this.  Your idea about using filters, such as 
camera filters, and a lightmeter could be a first approach in judging the 
relative intensities of “reds” versus “blues” or “greens”. A more precise 
approach would be to use a simple inexpensive spectrometer such as sold 
by Edmund Scientific in the USA.  I quote their description and website 


“Precision Economy Spectrometer
Accurate spectral measurement at a brilliant price!
Durable, hand-held plastic spectrometer that can be used to identify 
elements in flame spectra, solar spectra, and various lights (take a look 
at neon through them!). Easily calibrated to an accuracy within 1 
nanometer. Includes reference label for bright spectral lines.”

It seems this would be fine for analyzing street lights spectra. However, 
I don’t think that nocturnal light settings may not produce the intensity 
necessary for this device to produce useful spectra for the naked eye.  
You might tinker with using a small CCD camera or “WebCam” in conjunction 
with this spectrometer for additional sensitivity and record spectra to a 
PC. This may take some work with an imaging optic to focus the spectrum 
on the CCD. 

Beyond this one could move towards acquiring a CCD spectrometer.  
OceanOptics in Florida makes a fine series of such spectrometers.  They 
even award grants to high school and other institutions for light-based 
experimentation.  In the UK, they are particularly involved in deep sea 
imaging and spectrometry.  See their website…


And also this website on the recorded spectra of typical street lights…


Finally, it wouldn’t hurt for you to become more familiar with 
spectroscopy and spectra, in general.  There’s a “Beginner’s Corner” for 
that at these websites…




Good Luck Alex!

---* Dr. Ken Beck

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