Spectroscopy Study Guide

Spectroscopy Spectral analysis provides information about an object’s… a. Outer layer chemical composition of stars. b. Temperature of stars c. Movement of stars, if the distance between the star and the Earth is increasing or decreasing. (Doppler Effect – Red Shift, Blue Shift)

Spectroscopy e. Presence of magnetic fields d. Pressure of a star e. Presence of magnetic fields f. Condition of the gases in the star g. Size of the star

Spectroscope Spectroscope – the tool used to separate starlight into its colors. Is used for spectral analysis of stars.

Visible Light When visible light (white light) is passed through a prism a continuous spectrum is formed. Each color has a different wavelength. As a result each color is refracted (bent) a different amount. Elements radiate light into specific wavelength combinations that form banding patterns “fingerprints.”

Visible Light Rays of Sunlight Violet Indigo Blue Green Yellow Orange Ray bent most- shortest wavelength Spectrum of Colors Rays of Sunlight Violet Indigo Blue Green Yellow Orange Red Ray bent least- longest wavelength

Continuous Spectrum Unbroken band of colors – shows that its source is sending out light of all visible wavelengths.

Continuous Spectrum Sources - glowing solid, hot filament of light - glowing liquid, molten iron - hot compressed gases deep inside a star Example – incandescent light bulb

Bright Line Spectrum (Emission Spectrum) An unevenly spaced series of lines of different colors and brightness. The bright lines show the source is emitting light in certain wavelengths. I I I I I I I I I

Bright Line Spectrum (Emission Spectrum) Each element has its own unique bright-line spectrum. Clouds of hot gas around young stars produce emission lines. Example – Gas Tubes I I I I I I I I I

Dark-Line Spectrum (Absorption Spectrum) A continuous spectrum with dark lines where light is absorbed. These lines are called Fraunhofer Lines. I I I I I I I I

Dark-Line Spectrum (Absorption Spectrum) The dark lines are in the exact same spot as the same element in a bright-line spectrum. Forms when light passes through a cooler gas. The gas absorbs the same wavelengths, as it would give off if heated. Example – Star. I I I I I I I I

Dark-Line Spectrum (Absorption Spectrum) The position of the dark lines is used to identify the elements in the star. By looking at the dark-line spectrum of the sun more that 80 elements have been identified. Example – Sun I I I I I I I I