A Double-Slit Interference Experiment Is Performed in the Air

Multiple Choice

A double-slit interference experiment is performed in the air. Later, the same apparatus is immersed in benzene (which has an index of refraction of 1.50) , and the experiment is repeated.
When the apparatus is in benzene, you observe that the interference fringes are

A) equally spaced as when the apparatus is in air.
B) more closely spaced than when the apparatus is in air.
C) more widely spaced than when the apparatus is in air.