The distance of the path that in a vacuum would contain the same number of wavelengths as the actual path taken by a ray of light traveling through a medium.
‘For the interferometry to work, the optical paths have to be stable to fractions of a wavelength.’
‘Two tandem cells with a total optical path length of 1 cm were used for measuring the difference spectra.’
‘The compact nature of the photoreceptor mass requires the pigment screen to be extremely dense, as very short optical paths separate receptors from each other.’
‘The optical path difference is directly proportional to the cosine of the angle of refraction through the coating.’
‘The difference in optical path length is proportional to the difference in indices of refraction.’
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