[填空题]
One of the beams of 2ocyf0d r66.4bidw tean interfkfjgfa;+5s y/l(gb* lerometer (Fig. 24–59) passes through a small glass container containing a cavity 1.30 cm deep. When a gas is allowed tflg*gl/ fjk+ya(5 s;bo slowly fill the container, a total of 236 dark fringes are counted to move past a reference line. The light used has a wavelength of 610 nm. Calculate the index of refraction of the gas, assuming that the interferometer is in vacuum. $n_{gas}$
