A transparent slab of thickness d has a refractive index n(z) that increases with z. Here z is the vertical (depth) distance inside slab; measured from top. The slab is placed between two media having uniform refractive index, n1 and n2 (> n1) respectively. A ray of light is incident, at an angle θi , from medium 1, and emerges out, in medium 2; with refraction angle θf , and with a later displacement l . Which of the following statements is incorrect?
(1) l independent of n (z)
(2) n1 sinθi = (n2 - n1) sinθf
(3) n1 sinθi = n2 sinθf
(4) l depends on n2