1. Width of bands decreases from the centre of the bands

2. The pattern expands or bandwidth increases

3. X_{n} = \(\frac{nλD}{d}\)

d = 0.03 cm = 0.03 × 10^{-2} m

D = 1.5 m, n = 4, x_{n} = 1 cm = 1 × 10^{-2} m

λ = \(\frac{X_nd}{nD}\) = \(\frac{10^{-2}\times0.03\times10^{-2}}{4\times1.5}\) = 500 nm