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