The Mathematician Johann Jakob Balmer Found That the Formula $1 / \lambda=\mathrm{R}\left(1 / \mathrm{n}_{\mathrm{f}}^{2}-1 / \mathrm{n}_{\mathrm{i}}^{2}\right)$

Multiple Choice

The mathematician Johann Jakob Balmer found that the formula $1 / \lambda=\mathrm{R}\left(1 / \mathrm{n}_{\mathrm{f}}^{2}-1 / \mathrm{n}_{\mathrm{i}}^{2}\right)$ works for the hydrogen emission lines in the visible range, with what value of $n_{\mathrm{f}}$ ?

A) 1
B) 2
C) 3
D) 4
E) 5