dcsimg
ADVERTISEMENT

How Does a Spectrograph Work? [Infographic]

spectrograph, how does a spectrograph work, rainbow spectrum
spectrograph, how does a spectrograph work, rainbow spectrum



Illustration by George Retseck

A spectrograph splits light into its component wavelengths. First, light travels from a telescope through a small opening in the spectrograph to a collimating mirror that lines up all entering rays of light parallel to one another before they reach a finely scored plate of glass known as a diffraction grating. When light passes through or bounces off this glass grating, its many constituent wavelengths each change speed and direction according to their spectral color. The grating bends red light in a different way from orange light, which bends a little differently from yellow light and so on, spreading the many wavelengths into a rainbow spectrum. Rotating the diffraction grating controls which wavelengths of light reach another mirror, which in turn focuses these wavelengths onto a photodetector, such as a charge-coupled device. The detector converts photons into electrical signals that a computer interprets to measure the strength of different wavelengths.

How Does a Spectrograph Work, spectrograph, wavelength, rainbow spectrum
Image: Illustration by George Retseck

References:

http://outreach.atnf.csiro.au/education/senior/astrophysics/spectrographs.html#specobhow

http://spiff.rit.edu/classes/phys301/lectures/spectra/spectra.html

http://loke.as.arizona.edu/~ckulesa/camp/how_it_works.html

http://gratings.newport.com/library/handbook/chapter1.asp

Is The Milky Way A Cannibal? One Astronomer Travels to the Driest Place on Earth to Find Out

or subscribe to access other articles from the December 2012 publication.
Digital Issue $5.99
Digital Issue + Subscription $39.99 Subscribe
Share this Article:

Comments

You must sign in or register as a ScientificAmerican.com member to submit a comment.
ADVERTISEMENT