A point is situated at $7 c m$ and $7.2 c m$ from two coherent sources. Find the nature of illumination at the point if wavelength of light is $4000 ˚ A$ .

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Solution

Path difference, $Δ = 7.2 - 7 = 0.2 c m = 0.2 \times 10^{- 2} m$ , $λ = 4000 ˚ A = 4 \times 10^{- 7} m$
$p = \frac{2 Δ}{λ}$
$= \frac{2 \times 0.2 \times 10^{- 2}}{4 \times 10^{- 7}} = 10000$ .
Since $p$ is an even integer so the point is at the centre of the bright fringe.

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A point is situated at 7cm and 7.2cm from two coherent sources. Find the nature of illumination at the point if wavelength of light is 4000˚A.

Path difference, Δ=7.2−7=0.2cm=0.2×10−2m, λ=4000˚A=4×10−7mp=2Δλ =2×0.2×10−24×10−7=10000.Since p is an even integer so the point is at the centre of the bright fringe.

A point is situated at $7 c m$ and $7.2 c m$ from two coherent sources. Find the nature of illumination at the point if wavelength of light is $4000 ˚ A$ .

Path difference, $Δ = 7.2 - 7 = 0.2 c m = 0.2 \times 10^{- 2} m$ , $λ = 4000 ˚ A = 4 \times 10^{- 7} m$
$p = \frac{2 Δ}{λ}$
$= \frac{2 \times 0.2 \times 10^{- 2}}{4 \times 10^{- 7}} = 10000$ .
Since $p$ is an even integer so the point is at the centre of the bright fringe.