A line in the hydrogen spectrum occurs at 434 nm. what is the frequency of this radiation in sec - 1

The lines occurring in an emission spectrum are all electromagnetic waves, which means that their speed in a vacuum is

3 x 10⁸ m/s

We can use the equation,

v = fλ

which relates the velocity of a wave to the frequency and wavelength. Substituting values,

3 x 10⁸ = f * 434 x 10⁻⁹

f = 6.91 x 10¹⁴ Hz

The frequency of the wave will be 6.91 x 10¹⁴ oscillations per second.