What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition n = 4 to n = 2 of He⁺ spectrum?

The decreasing order of electron affinity of F, Cl, Br is F > Cl >Br

The basic nature of the hydroxides of group 13 (Gr. III B) decreases progressively down the group.

The dipole moment of CH₃F is greater than of CH₃Cl