1. Width of bands decreases from the centre of the bands
2. The pattern expands or bandwidth increases
3. Xn = \(\frac{nλD}{d}\)
d = 0.03 cm = 0.03 × 10-2 m
D = 1.5 m, n = 4, xn = 1 cm = 1 × 10-2 m
λ = \(\frac{X_nd}{nD}\) = \(\frac{10^{-2}\times0.03\times10^{-2}}{4\times1.5}\) = 500 nm