Optical methods

Techniques that exploit the wave nature of light for measuring temperature are described here. Radiation that belongs to the visible range of the electromagnetic spectrum (wavelength) is referred to light. Optical effects are associated primarily with the electrical field rather than the magnetic field. Hence the propagation of light originating from a conventional light source is expressible as

Here E is the electrical field, is its amplitude corresponding to a wavelength is the phase associated with the harmonic, is the speed of light and and are time and distance respectively. For a monochromatic source, only one wavelength is significant, phase may be set to zero, and