Presentation on theme: "Spectroscopy The study of light emissions and absorptions."— Presentation transcript:
Spectroscopy The study of light emissions and absorptions
The Visible Spectrum
Newtons Colour Wheel
Dispersion of White Light
Creating a Spectrum
Atomic Emission Lines An emission line is formed when an electron makes a transition from a particular discrete energy level of an atom, to a lower energy state, emitting a photon of a particular energy and wavelength. A spectrum of many such photons will show an emission spike at the wavelength associated with these photons.
Atomic Emission Principles When the electrons in the element are excited, they jump to higher energy levels. As the electrons fall back down, and leave the excited state, energy is re- emitted, the wavelength of which refers to the discrete lines of the emission spectrum.
Electron Excitation The Hydrogen Atom
Hydrogen Tube and Emission Bands
Emissions from an elemental gas
Emission Spectrum - H
Emission Spectrum - He
Emission Spectrum - Na
Emission Spectrum - Fe
Fireworks Red - Strontium and Lithium salts Orange - Calcium salts Yellow - Sodium salts
Fireworks Green - Barium salts Blue - Copper salts Gold - incandescence of iron and charcoal White - white hot metals
Atomic emissions beyond the visible spectrum Note that the emission extends over a range of frequencies. The term often refers to the visible light emission spectrum, although it extends to the whole electromagnetic spectrum, from the low energy radio waves up to high energy gamma rays.
Atomic Absorption Lines An absorption line is formed when an electron makes a transition from a lower to a higher discrete energy state, with a photon being absorbed in the process. These absorbed photons generally come from background continuum radiation and a spectrum will show a drop in the continuum radiation at the wavelength associated with the absorption.
Comparing different spectra
Astronomical Spectroscopy Involves the scientific exploration and analysis of the properties of distant objects Involves the observation of spectra at very high spectral resolutions
Astronomical Spectroscopy Chemical elements can be detected in astronomical objects by their emission lines and absorption lines The shifting of spectral lines can be used to measure the redshift or blueshift of distant or fast-moving objects Helium was first discovered by spectral analysis of light from the Sun
Absorption Spectrum of the Sun
Hydrogen Absorption Spectrum
Origins of different Spectra
The Sun - A Nuclear Reactor
Formation of Deuterium as per The Big Bang
Hydrogen Fusion in Stars
Nuclear Fusion to form Helium - another possible mechanism