[填空题]
A micrometer is connected to the movable mirror of an intec91c dwhb /lr9rferometer. When th6jj zj, s8jmk pxdk00(e micrometer is tightened down on a thin metal foil, the net number of bright fringes that move, compared to the empty micrometer, is 272. Wha6m,z(sjjd0kj8 0xj kp t is the thickness of the foil? The wavelength of light used is 589 nm. $\mu m$
