Session 1, Page 17: Session Review

Glossary:
Absorption lines	- dark lines in a continuous spectrum of white light caused by absorption by a gaseous element. The lines correspond to the same light frequencies that would be emitted by the gaseous element.
Continuous spectrum	- one which shows continuous non-discrete changes of intensity with wavelengths or particle energy.
Diffraction	- the spreading out of light passing through an aperture or opening or opaque object
Diffraction Grating	- optical device made of glass or metal etched with thousands of closely-spaced lines . The grooves produce interference patterns in light. There are two types; transmission gratings allo the light to pass through, while reflection gratings reflect the light away.
Dispersion	- the dependence of wave velocity on the frequency of wave motion; a property of the medium in which the wave is propagated. In the visible region of the electromagnetic spectrum, dispersion manifests itself as the variation of refractive index of a substance with wavelength (colour) of the light. It is on account of its dispersion that a prism is able to form a spectrum.
Emission line spectrum	- a spectrum that contains bright emission lines
Reflection	- the return of light rays by a surface
Refraction	- bending of light rays when they pass from one transparent medium to another
Spectrograph	- an instrument for photographing a spectrum
Spectrometer	- any device that produces a spectrum by dispersion and is calibrated to measure transmitted energy with respect to wavelengths of radiation, refractive indices of prism materials, or radiant intensities at various wavelengths.
Spectroscope
Spctroscopy	- the analysis of the ways in which matter emits and absorbs radiation
Spectrum	(1) A distribution of entities or properties arrayed in order of increasing or decreasing magnitude. For example, a beam of ions passed through a mass spectrograph, in which they are deflected according to the charge-to-mass ratios, will have a range of masses called a mass spectrum. A sound spectrum is the distribution of energy over a range of frequencies of a particular source. (2) A range of electromagnetic energies arrayed in order of increasing or decreasing wavelength or frequency. The emission spectrum of a body or substance is the characteristic range of radiations it emits when it is heated, bombarded by electrons or ions, or absorbs photons. The absorption spectrum of a substance is produced by examining, through the substance and through a spectroscope, a continuous spectrum of radiation. The energies removed form the continuous spectrum by the absorbing medium show up as black lines or bands. With a substance capable of emitting a spectrum, these are in exactly the same positions in the spectrum as some of the lines and bands in the emission spectrum. Emission and absorption spectra may show a continuous spectrum, a line spectrum or a band spectrum. A continuous spectrum contains an unbroken sequence of frequencies over a relatively wide range; it is produced by incandescent solids, liquids and compressed gases. Line spectra are discontinuous lines produced by excited atoms and ions as they fall back to a lower energy level. Band spectra (closely grouped bands of lines) are characteristic of molecular gases or chemical compounds.
Wavelength	- the horizontal distance between crests of two adjacent waves.

	Introduction to Solar Observing	Course Overview	Course Syllabus	Course Schedule
	Introduction to Solar Observing	Index of Course Sessions