Data : λ1 = 6000 Å = 6 × 10-7 m, λ2 = 4800 Å = 4.8 × 10-7 m, W1 = 0.32 mm = 3.2 × 10-4 m.
Distance between consecutive bright fringes,
∴ ∆W = W1 – W2
= 3.2 × 10-4 m – 2.56 × 10-4 m
= 0.64 × 10-4 m
= 6.4 × 10-5
= 0.064 mm
This is the required change in distance.