A transparent slab of thickness d has a refractive index n(z) that increases with z. Here z is the vertical distance inside the slab, measured from the top. The slab is placed between two media with uniform refractive indices n1 and  n2 (>n1) , as shown in the figure. A ray of light is incident with angle  θi from medium 1 and emerges in medium 2 with refraction angle θf  with a lateral displacement l.Which of the following statement (s) is (are) true?