[" At the first minimum adjacent to the central "],[" maximum of a single-slit diffraction pattern,"],[" the phase difference between the Huygen's "],[" wavelet from the edge of the slit and the "],[" wavelet from the edge of the slit and the "],[" wavelet from the midpoint of the slit and "],[" (a) "pi" radian "],[" (c) an astronomical telescope in normal "L],[" adjustment a stride part of objective lens.The The "],[" eye-piece forms a real image of this line.The "],[" exgth of this image is "I" .The magnificatior "]