In a H–atom, the transition takes place from L to K shell. If R = 1.08 × 10⁷m^–1, the wave length of the light emitted is nearly

For K and L shell corresponding principal quantum number is n=1 and n=2.
Transition is from n₂​=2 to n₁​=1

$\frac{1}{\lambda }=R\left[\frac{1}{n_1^2}-\frac{1}{n_2^2}\right]$

Substituting n ₁​=1, n ₂​=2 and R=1.09×10 ⁷m ⁻¹.

$\lambda =\frac{4}{3R}=1250A°$