Download Spectroscopy Study Guide

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
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
Spectrum
of Colors
Ray bent mostshortest
wavelength
Violet
Indigo
Blue
Green
Yellow
Orange
Red
Ray bent leastlongest
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.
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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
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Dark-Line Spectrum
(Absorption Spectrum)
• A continuous spectrum with dark lines
where light is absorbed.
• These lines are called Fraunhofer Lines.
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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.
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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
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