Question

The slits in Young?? double slit experiment are illuminated by light of wavelength $6000 ?$. 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)

$2.4\times 10^{-6}m$

Answer 2

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 $= 4 \times 6000 \times 10^{-10}$ $= 24 \times 10^{-7}$ $= 2.4 \times 10^{-6}\, m$