The emission spectra of He⁺ ions show 6 different photons. What will be the minimum wavelength during the transition? (R_H = Rydberg constant)

n(n−1)/2 = 6 → n = 4. Minimum wavelength → maximum energy → transition from n=4 to n=1. 1/λ = R_H × Z² × (1/n₁² − 1/n₂²) = 4R_H(1 − 1/16) = 4R_H × 15/16. λ = 4/(15R_H)