Explain+the+important+elements+of+Spectroscopy+and+their+uses


 * Succinct milestone description**:

Explain the important elements of Spectroscopy and their uses.


 * Milestone discussion:**

Spectroscopy is used in astronomy to measure the chemical composition and physical properties of celestial objects or to measure their velocities using the redshift of their spectral lines.

There are three types of spectra—continuous, emission line, and absorption line. · A continuous spectrum includes all wavelengths of light and is produced by a dense object that is hot, either a dense gas (such as a star) or a liquid or solid. · An emission line spectrum consists of light at only a few wavelengths and is produced by a hot, tenuous (low-density) gas. The wavelengths of the emission lines depend on the type of gas that produced them. For example, Hydrogen produces different emission lines from Helium. · Absorption lines can be thought of as the opposite of emission lines. Whereas emission lines add light of particular wavelengths, absorption lines subtract light of particular wavelengths. Absorption lines are produced by a cool gas and can only be seen when superimposed onto a continuum spectrum. A spectrograph is an instrument that transforms an incoming time-domain waveform into a frequency spectrum, or generally a sequence of such spectra. Modern spectrographs use electronic detectors, such as CCDs which can be used for both visible and UV light. When light enters a spectrograph, it is bounced off one mirror, onto a grating, onto another mirror, and then onto a detector which produces a graph.