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The optical path difference between the paths taken by two identical waves can then be used to find the phase change. Finally, using the phase change, the interference between the two waves can be calculated. Fermat's principle states that the path light takes between two points is the path that has the minimum optical path length.
When the two waves are in phase, i.e. the path difference is equal to an integral number of wavelengths, the summed amplitude, and therefore the summed intensity is maximal, and when they are in anti-phase, i.e. the path difference is equal to half a wavelength, one and a half wavelengths, etc., then the two waves cancel, and the summed ...
This then leads to a phase difference between the light passing in the two vibration directions of = (/). For example, if the optical path difference is λ / 2 {\displaystyle \lambda \,/2} , then the phase difference will be π {\displaystyle \pi } , and so the polarisation will be perpendicular to the original, resulting in all of the light ...
In addition the ray reflected from the bottom plate undergoes a 180° phase reversal. As a result, at locations (a) where the path difference is an odd multiple of λ/2, the waves reinforce. At locations (b) where the path difference is an even multiple of λ/2 the waves cancel.
This path difference is (+) (′). The two separate waves will arrive at a point (infinitely far from these lattice planes) with the same phase , and hence undergo constructive interference , if and only if this path difference is equal to any integer value of the wavelength , i.e. n λ = ( A B + B C ) − ( A C ′ ) {\displaystyle n\lambda ...
When the two waves are in phase, i.e. the path difference is equal to an integral number of wavelengths, the summed amplitude, and therefore the summed intensity is maximum, and when they are in anti-phase, i.e. the path difference is equal to half a wavelength, one and a half wavelengths, etc., then the two waves cancel and the summed ...
The main central beam, nulls, and phase reversals are apparent. Graph and image of single-slit diffraction. As an example, an exact equation can now be derived for the intensity of the diffraction pattern as a function of angle in the case of single-slit diffraction. A mathematical representation of Huygens' principle can be used to start an ...
A common misconception occurs between phase velocity and group velocity (analogous to centres of mass and gravity). They happen to be equal in non-dispersive media. In dispersive media the phase velocity is not necessarily the same as the group velocity. The phase velocity varies with frequency.