题目

如图是一束单色光从某一介质进入空气介质中发生的现象，已知光在空气中的速度为c，则该单色光在该介质中的波速为 ( )A. c B. C. D. 答案：【答案】D【解析】由图可知，入射角i=30°，折射角为r=60°，则该介质的折射率为：，该单色光在该介质中的波速为：，故D正确，ABC错误。— How do you find the concert in the Beijing Grand Theatre last night?     — _______．But the conductor was perfect.               A．I don’t think much of it         B．I couldn’t agree more        C．I was crazy about it  D．I really like it