During an annular eclipse, the moon covers only the central part of the sun's disk, leaving a ring of sunlight still visible.
在日环食发生的时候，月亮仅仅遮挡住了太阳光晕的中间部分，在外侧留下一圈可见的光环。
2
The annular magnet is embedded into an inner cavity of the rubber ring, the plastic cover disk is covered at the back face of the rubber ring.
将环形磁铁嵌入橡胶圈的内腔中，再将塑料罩盘盖在橡胶圈的背面。
3
The amplitude and intensity analytic expressions for disk (sphere) and annular aperture Fresnel diffraction are given on the base of scalar diffraction theory.