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The above is an attempt to render the visible spectrum on
your monitor. Different wavelengths of light
(λ, from .380 μm to .750 μm) are
seen by the human eye as different colors
(V=violet, B=blue, G=green, Y=yellow, O=orange, R=red).
In the previous quiz, plots like the above displayed the
amount of light energy as a function of wavelength as a smooth curve.
But in fact stellar spectra (and the spectra of essentially all real objects)
differ from the ideal blackbody.
Much of this quiz will deal with the spectra of real objects as observed in class
with the Project STAR spectrometer:
If we restrict our plots of sunlight to just the wavelengths of light visible to the human eye,
we can line up what you would see with the spectrometer (reversed
so things are in a consistent order),
an idealized version of the spectrum (from Wiki), and an actual plot of energy flux.
A B C D
Notice that sunlight (true "white" light) is a mixture of an approximately equal
amounts of light at every wavelength detectable by the human eye.
The human eye is a poor color detector (in the sense that actually different light
looks the same to us). Unlike
a radio receiver which can separately detect any given radio station (e.g.,
KNSR 88.9 MHz, KSJU 90.1 MHz, etc.), your eye maps the entire visible band into just three "stations":
the light detected by the L, M, and S cone cells in your retina (very approximately detecting
the colors we call yellow, green, and blue).
Using an analogy to sound: imagine an ear to which all the lower third keys on a piano
are indistinguishable, the middle third can be distinguished from the lower
third, but not each other, and finally a top third. Imagine what a concert
would sound like to such an ear, and you can get an idea of how much nuance
in light is missed by the human eye! Things that look the same to your eye, can
in fact be quite different; the spectrometer can display that difference.
Parking lot lighting aims for cheap illumination ---
not comfortable reading or accurate color presentation.
Thus you'll find widely deviant lighting sources outside the home.
The above spectra, as seen through our classroom spectrometer,
shows of a low pressure sodium lamp used for outdoor illumination.
A B C D E F
A B C D E