[填空题]
When a Newton’s ring apparatus (Fig. *zw;r. fquzutt(4 * wv24–31) is immersed in a liquid, the diametez;(z4ftww .rtq* v* uuw ;* ce 1e6 dzz3zroyp)f-v-yer of the eighth dark ring decreases from 2.92 cm to 23)co rz-1e-v*dfe;6eyzpw zy .48 cm. What is the refractive index of the liquid?
