The principles and methods of geometrical optics : especially as applied to the theory of optical instruments / by James P. C. Southall.

Southall, James P. C. (James Powell Cocke), 1871-1962.

Date:: 1913

Credit: The principles and methods of geometrical optics : especially as applied to the theory of optical instruments / by James P. C. Southall. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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$back from A' in the direction exactly opposite to that by which it arrived, it will return over precisely the same route in the reverse order and arrive finally at A again. 19. The Laws of Reflexion and Refraction as derived by the Wave-Theory (Huygens's Construction). A plane wave travelling in an isotropic medium advances with uniform speed and without change Fig. 6. Huygens's Construction of the Reflected and Refracted Wave-Fronts in the Case of a Plane Wave Incident on a Plane Surface, w is a section in the plane of incidence (plane of paper) of a plane surface separating the first medium {a) from the second medium {b). The straight lines AB, CG and C/fare the traces in the plane of the paper of the incident, reflected and refracted wave-fronts. of form along the direction of the normal to its plane, so that the rays are parallel to each other and perpendicular to the plane wave- front. If the wave-front arrives at a smooth geometric surface sepa- rating the first medium (a) from another isotropic optical medium (b), the refracted wave proceeding into this second medium will, in general, be changed both in form and in direction. At the same time also a$