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