Wave length for which maxima occurs
\(2 \mu t \cos r=(2 n-1) \frac{\lambda}{2}\)
\(\lambda=\frac{4 \mu t \cos r}{2 n-1}\)
\(r=0, \lambda=\frac{4 \mu t}{2 n-1}\)
for \(n=2\)
\(\lambda=\frac{4(3100)}{3} \times \frac{4}{3}\)
\(=5511.11 \,\mathring A\)
(Wavelength of yellow)