Those of you who are physicists, I hear you rolling your eyes, but bear with me.  To measure the wavelength, all I need to do is measure the distance from here -- one full wave -- over to here.
对于在座的物理学家们，我知道你们感到很无聊， 但你们也就忍一忍吧。（众笑） 要测量波长， 我只要测量从这里 到这里，一整段波的长度。