_energy levels and spectra ppt chsb a39level physics35能级和光谱ppt和胆脂瘤39级物理课件

3.5 Energy levels and spectra DISPERSION 3.5 Energy levels and spectra DISPERSION White light (from the sun or a lamp) is made up of different colours. Raindrops or glass will separate these colours into a continuous spectrum from about 400nm to 650nm. This is called dispersion. 3.5 Energy levels and spectra Line spectra discrete: coloured lines due to photons of certain energies only Using a tube of glowing gas produces a line spectrum of discrete colours whose wavelengths are unique to the elements excited atoms energy levels . Using a tube of glowing gas produces a line spectrum of discrete colours whose wavelengths are unique to the elements excited atoms energy levels . The photons producing each line all have the same energy. Using a tube of glowing gas produces a line spectrum of discrete colours whose wavelengths are unique to the elements excited atoms energy levels . The photons producing each line all have the same energy. Each photon is emitted when an atom de-excites from a higher energy level to a lower energy level. Energy of emitted photon = hf = E1- E2 Continuous spectra: Continuous spread of wavelengths due to a continuous spread of photon energies Band spectra: a fine structure is produced by the energies of chemical bonds in the molecules Continuous spectra: Continuous spread of wavelengths due to a continuous spread of photon energies Band spectra: a fine structure is produced by the energies of chemical bonds in the molecules Continuous spectra: Continuous spread of wavelengths due to a continuous spread of photon energies Band spectra: a fine structure is produced by the energies of chemical bonds in the molecules Continuous spectra: Continuous spread of wavelengths due to a continuous spread of photon energies Band spectra: a fine structure is produced by the energies of chemical bonds in the molecules In the solar spectrum there is strong absorption at wavelengths corresponding to the emission spectra of hydrogen and helium This shows the presence of these elements in the hot gas around the sun. E = 0 eV E = 13.6 eV E = 0 eV E = 13.6 eV visible E = 0 eV E = 13.6 eV uv visibleir E = 0 eV E = 13.6 eV uv visibleir Energy of an emitted photon = 1 _ 1 x 13.6eV n22 n12 E = 0 eV E = 13.6 eV Energy of emitted photon = hf = E1- E2 Energy of emitted photon = hf = E