Rayleigh distance Rayleigh distance Rayleigh distance in optics is the axial distance from a radiating aperture to a point at which the path difference between the axial ray and an edge ray is λ / 4. An approximation of the Rayleigh Distance is formula_1, in which Z is the Rayleigh distance, D is the aperture of radiation, λ the wavelength. This approximation can be derived as follows. Consider a right angled triangle with sides adjacent formula_2, opposite formula_3and hypotenuse formula_4. According to Pythagorean theorem, formula_5. Rearranging, and simplifying formula_6 The constant termformula_7 can be neglected. In antenna applications, the Rayleigh distance is
Bowditch Crests Bowditch Crests Bowditch Crests () is a line of precipitous cliffs surmounted by four summits on Bermel Peninsula in eastern Graham Land. The feature was photographed from the air by Lincoln Ellsworth in November 1935 and was mapped from these photos by W.L.G. Joerg. It was surveyed by the Falkland Islands Dependencies Survey in 1958, and named by the UK Antarctic Place-Names Committee for Nathaniel Bowditch, American astronomer and mathematician, author of "The New American Practical Navigator" (1801) which firmly set out the practical results of theories established at that date and has since gone through more than 56 editions.