See, to believe

The easiest spectroscopy is the optical one. If you see you believe!

The human eye is rather blind, compared to the ear: it senses only one octave of frequencies (380-760 nm) compared to 8 octaves of the ear (50-20000 Hz). But it is well adapted to our Star emission spectrum.

First systematic investigations of spectra were done by Bunsen and Kirchhoff between 1855 and 1863.
http://physics.kenyon.edu/EarlyApparatus
/Optics/Spectrometers/Spectrometers.html

Spectrum of the Solar Radiation: 
UV- ultraviolet, VIS- visible radiation, NIR – near infrared
Adapted from:
http://eetd.lbl.gov/coolroof/intro.htm, Lawrence Berkeley NL, USA

To see a spectrum, anything is good: “chromatographic” glasses, professional 
spectrometer or even a CD-grating.

That of hydrogen, is the simplest with only 4 lines in the visible range. 
But they were so important for quantum mechanics… 

The spectrum of the 10-electron atom, neon, is already quite complicated. 
Neon flashes in red, but its spectrum contains green and blue, as well.

The human eye is adapted to the Solar 
spectrum: rods are most sensitive in 
its maximum

The human eye posses two types of 
receptors: rods for black and white vision and cones for colours, with three types of spectral sensitivity.

Optical spectroscopy can be divided into: emission, absorption, and fluorescence. What is the “real colour” , is not a trivial question.

Emission spectrum of the “energy-saving” fluorescent lamp

Absorption and fluorescence spectrum of an ice-cream spoon

What we see, we believe. But even if we do not see, we must believe.

What is above the visible light, we call under-red, what is below: above-violet.

You can not see the infrared but your digital camera can.

You do not feel ultraviolet, but these plastics (and Your skin) does.

[1] Silke Stach, Julie Benard and Martin Giurfa, Local-feature assembling in visual pattern recognition and generalization in honeybees, 
Nature 429, 758-761 ( 2004)