Question

The slits in Young’s double slit experiment are illuminated by light of wavelength $6000 \,\mathring{A}$. If the path difference at the central bright fringe is zero, what is the path difference for light from the slits at the fourth bright fringe?

• A. $2.4\times 10^{-6}m$
• B. $1.2\times 10^{-6}m$
• C. $10^{-6}m$
• D. $ 0.5 \times 10^{-6}m$

Answer 1

Answer: (A)

The path difference at the centre is zero.
The path difference at the $4^{th}$ bright fringe $= 4\lambda$
Here, $\lambda = 6000 \times 10^{-10}\, m$
$\therefore $ Path difference $= 4 \times 6000 \times 10^{-10} $
$= 24 \times 10^{-7}$
$= 2.4 \times 10^{-6}\, m$