Given:
x1 = 6.5 cm = 6.5 x 10-2 m,
x2 = 6.65 cm = 6.65 x 10-2 m,
λ = 5000 Å = 5 x 10-7 m
To find : Nature of illumination at the point
Formula: Δ x = n λ
Calculation: Path difference is given by,
Δ x = x2 - x1 = 6.665 x 10-2 - 6.5 x 10-2 = 0.15 x 10-2 m
From formula,
n = \(\frac{Δx}{λ}\)
n = \(\frac{0.15\times10^{-2}}{5\times10^{-7}}\)
= 3000
∴ Δ x = 3000λ = 6000\(\frac{λ}{2}\)
As the path difference is even multiple of \(\frac{λ}{2}\) , the point is bright.
Ans: The point is bright.