通常的实验室光源选用汞弧灯.A common laboratory source of light is provided by a mercury arc.不很精确的射电干涉仪观测表明,这个源的角径约为1.5弧秒.Comparatively rudimentary interferometer observations suggested that this source is about 1.5 across.单个弧是不能求长的.T...

“弧缘”的英语可以翻译为：[医][单]lunula，[复]lunulae ...