Question

Light considering of wavelengths $6000\stackrel{{}^{\circ }}{A}$ and $5500\stackrel{{}^{\circ }}{A}$ falls on the double slits in $YDSE$ . $n^{\text{th }}$ order bright fringe of $\lambda =6000\stackrel{{}^{\circ }}{A}$ is found to coincide with the $m^{\text{th }}$ order bright fringe of $\lambda =5500\stackrel{{}^{\circ }}{A}$ . Smallest values of $n$ and $m$ are respectively

• A. $22,23$
• B. $11,12$
• C. $7,9$
• D. $15,17$

Answer 1

Answer: (B)

$n\lambda =m{\lambda }^1$
$\frac{n}{m}=\frac{{\lambda }^1}{\lambda }=\frac{5500}{6000}=\frac{11}{12}$