Chapter 24 Studying the Sun Section 1 The 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 Gamma rays to radio waves Organized in the electromagnetic spectrum 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 It has a wavelength and a wave height Can be separated into separate colors and wavelengths by a prism

Electromagnetic Radiation In some cases, light acts like a stream of particles called photons Small bullets from a machine gun They push matter The force they exert is called radiation pressure Photons from the sue cause the tail of the comet Shorter wavelengths have more energetic photons and longer wavelengths have less energy

Spectroscopy Study of the properties of light that depend on wavelength Sir Isaac Newton used a prism to separate light into its component colors ROY G BIV Continuous Spectrum Made by an incandescent solid, liquid or gas under pressure Uninterrupted band of color Comes from an incandescent

Spectroscopy Absorption Spectrum Visible light passes through a cool gas under low pressure Gas absorbs some wavelengths Continuous spectrum with dark lines running through it

Spectroscopy Emission Spectrum Important Produced by hot gases under low pressure Bright lines of particular wavelengths Important Each element or compound has a unique set of spectra lines These lines act as fingerprints They show which elements or compounds are present in a star

Emission Spectrum

Spectroscopy Sun’s spectrum Has thousands of dark lines 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. Moving toward an object causes the wavelengths to push together and become shorter Blue Shift Moving away from an object causes the wavelengths to spread apart and become longer Red Shift 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 Larger the shift; the faster the speed Smaller the shift; the slower the speed Compare the absorption spectrum to the standard spectrum produced in a lab

Doppler Shift