The spectrum of white light ranges from
(a)15 x 1014 Hz to8 x 1014 Hz
(a)7.5 x 1014 Hz to4 x 1014 Hz
(a)3.5 x 1014 Hz to2 x 1014 Hz
(a)6 x 1014 Hz to3 x 1014 Hz
Take a look at the spectrum of electro - magnetic spectrum
We can see the visible spectrum is