Balmer's Constant

Balmer's Constant is used in chemistry to discern the frequency of light emitted when an atom's electron returns to the ground state. It can also be used to find the frequency of light necessary to excite an speed of light in a vacuum). It is used in the formula:

${\nu}=C\left(\frac{1}{n_i^2}-\frac{1}{n_f^2}\right) \$ .