An observer can see through a small hole on the side of a jar (radius 15 cm ) at a point at height of 15 cm from the bottom (see figure). The hole is…

An observer can see through a small hole on the side of a jar (radius $\displaystyle 15$ cm ) at a point at height of $\displaystyle 15$ cm from the bottom (see figure). The hole is at a height of $\displaystyle 45$ cm. When the jar is filled with a liquid up to a height of $\displaystyle 30$ cm the same observer can see the edge at the bottom of the jar. If the refractive index of the liquid is N/$\displaystyle 100$, where N is an integer, the value of N is \_\_\_\_.