Distinguishing The Different Terms

The Chemistry of Art > 2. The Structure of the Atom and Colours > Distinguishing The Different Terms >

Distinguish between the terms spectral line, emission spectrum, absorption spectrum and reflectance spectrum

Spectrum: introduced by Isaac Newton in describing a phenomenon that white light (coming from the sun) consists colors in wide range (component wavelengths)

Spectrometer: Instrument used for the analysis of spectrum which commonly composed of source, sample holder, slit, dispersion device and detector

Spectral lines:

  • Individual wavelengths of light on a emission or absorption spectrum
  • Achieved through passing emitting light from an atom through a prism or diffraction grating
  • Unique for a given material
  • Provides information about the abundance of elements

Emission Spectrum:

  • A type of spectrum produced when electrons of an atom that have been excited to higher energy levels release photons as they return to lower energy levels
  • In the instrumentation, white lights passed through a material in hot atomic gaseous form
  • The wavelengths of the released light varies depending on the change in energy level of electrons
  • Appears as discrete coloured spectral lines on black background separated by blank areas
  • The emission lines in the spectrum are the characteristics of the composition of gas
  • Using a spectroscope, this spectrum can be utilized in the qualitative and quantitative detection of elements

Absorption Spectrum:

  • Produced when atoms absorb photons of particular wavelengths and become excited to higher energy levels
  • In the instrumentation, white light passed through substance in cold vapor phase
  • Appears as black spectral lines within full spectrum
  • In the analysis of pigment, the intensity of absorption gives information about the quantity of pigment, while the shape of absorption band gives details on purity of pigment

Reflectance Spectrum:

  • Provides information about the colours of light being reflected by a material
  • Substance exhibits colour complementary to that color of absorbed
  • The spectrum is produced upon shining of object with white light