A double-slit interference experiment is conducted in air using monochromatic light of wavelength \(\lambda_0\). The slits have separation \(d\) and individual width \(a\), where \(d > a\), and the pattern is observed on a screen at distance \(L\). The entire apparatus is then immersed in a transparent oil with index of refraction \(n > 1\). Which of the following correctly describes the change in the fringe spacing \(\Delta y\) on the screen and the change in the number \(N\) of bright interference fringes contained within the central diffraction envelope?