Chapter 24Studying the Sun
Section 1The Study of Light
Notes 24-1
Vocabulary• Electromagnetic spectrum• Photon• Spectroscopy• Continuous spectrum• Absorption spectrum• Emission spectrum• Doppler Effect
Electromagnetic Radiation• All different types of wavelengths of energy
o Gamma rays to radio waveso Organized in the electromagnetic spectrumo All energy travels at the same speed through a vacuum =
300,000 km per sec
Electromagnetic Radiation• Light can behave like a wave or a particle
o It has a wavelength and a wave heighto Can be separated into separate colors and wavelengths by
a prism
Electromagnetic Radiation• In some cases, light acts like a stream of particles
called photonso Small bullets from a machine guno They push matter• The force they exert is called radiation pressure• Photons from the sue cause the tail of the comet
o Shorter wavelengths have more energetic photons and longer wavelengths have less energy
Spectroscopy• Study of the properties of light that depend on
wavelengtho Sir Isaac Newton used a prism to separate light into its
component colors o ROY G BIV
• Continuous Spectrumo Made by an incandescent solid, liquid or gas under
pressureo Uninterrupted band of coloro Comes from an incandescent
Spectroscopy• Absorption Spectrum
o Visible light passes through a cool gas under low pressureo Gas absorbs some wavelengthso Continuous spectrum with dark lines running through it
Spectroscopy• Emission Spectrum
o Produced by hot gases under low pressureo Bright lines of particular wavelengths
• Importanto Each element or compound has a unique set of spectra
lineso These lines act as fingerprintso They show which elements or compounds are present in a
star
Emission Spectrum
Spectroscopy• Sun’s spectrum
o Has thousands of dark lineso More than 60 elements have been identified in the sun
Doppler Effect• The perceived change in wavelength of a wave that is
emitted by source that is moving away or toward an object.o Moving toward an object causes the wavelengths to push together and
become shorter• Blue Shift
o Moving away from an object causes the wavelengths to spread apart and become longer• Red Shift
o Used to determine if a star or bright object is moving away or towards the observer• Amount of shift depends on the rate at which it occurs
o Larger the shift; the faster the speedo Smaller the shift; the slower the speed
• Compare the absorption spectrum to the standard spectrum produced in a lab
Doppler Shift