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 The Crests The Crests were an American doo-wop group, formed by bass vocalist J.T. Carter in the mid 1950s. The group had several Top 40 hits in the late 1950s and early 1960s on Coed Records. Their most popular song, "16 Candles", rose to #2 on the "Billboard" Hot 100 chart in February 1959 selling over one million copies and earning a gold disc status. The group's other hits include "Step By Step", "The Angels Listened In", "Trouble In Paradise", "Six Nights A Week", and "A Year Ago Tonight". The Crests were the first interracially mixed doo-wop group, consisting of