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
What Is This Thing Called Love? (short story) What Is This Thing Called Love? (short story) "What Is This Thing Called Love?" is a science fiction short story by Isaac Asimov. The story was requested by Cele Goldsmith Lalli, editor of "Amazing Stories", as a satire of an article in "Playboy" called "Girls of the Slime God" which had suggested that pulp science fiction stories were concerned with aliens and sex. The story appeared in the March 1961 issue of "Amazing" as "Playboy and the Slime God", but Asimov later retitled it "What Is This Thing Called Love?" According to Asimov, in "1938-39 ... for some half a