Question

A point is situated at 6.5 em and 6.65 em from two coherent sources. Find the nature of illumination at the point, if wavelength of light is 5000 Å

Answer 1

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 = nλ

Calculation: Path difference is given by

Δx = x₂ - x₁ = 6.65 x 10^-2 - 6.5  10^-2

= 0.15 x 10^-2 m

From formula,

n = `(trianglex)/lambda`

n = `(0.15 xx 10^(-2))/(5xx10^(-7))`

= 3000

∴ Δx = 3000λ   = 6000 x λ/2

As the path difference is even multiple of λ/2

∴ The point is bright.