Interference fringes are observed on a screen by illuminating two… - Vidyadip

MCQ

Interference fringes are observed on a screen by illuminating two thin slits $1 \,mm$ apart with a light source $(\lambda=632.8\, nm )$. The distance between the screen and the slits is $100\, cm$. If a bright fringe is observed on a screen at a distance of $1.27\, mm$ from the central bright fringe, then the path difference between the waves, which are reaching this point from the slits is close to$....\mu m$

✓
$1.27$
B
$2$
C
$2.87$
D
$2.05$

✓

Answer

Correct option: A.

$1.27$

a
$y=\frac{n D \lambda}{d}$

$n=\frac{y d}{D \lambda}=\frac{1.27 \times 10^{-3} \times 10^{-3}}{1 \times 632.8 \times 10^{-9}}=2$

Path difference $\Delta x=n \lambda$

$=2 \times 632.8 nm$

$=1265.6 nm$

$=1.27 \mu m$

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