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
The Crests charted with their first release, "Sweetest One", on Joyce Records. After recording two more singles for Joyce Records, Patricia Vandross left The Crests in 1958 to finish her education. Their next single after "16 Candles" on COED Records was "Six Nights A Week" which hit #28 on the "Billboard" Hot 100 Charts and #17 on the R&B. Their next release "Flower Of Love" was bland compared to other Crests cuts and attained only a six-week run-up to #79. From 1958 to 1960 the group was almost always on the road. In the late 1950s, The Crests performed on several national