Avisible violet light emits light with a wavelength of 4.00 × 10-7 m. calculate the frequency of the violet light.

For any wave,             
                           Frequency = (speed) / (wavelength)

                                              = (3 x 10⁸ m/s) / (4 x 10⁻⁷ m)

                                              = (3/4 x 10¹⁵)  ( m / m - s )

                                              = (0.75 x 10¹⁵)  /sec

                                              =  7.5 x 10¹⁴  Hz

                                              =   750,000 GHz 

                  

Ibelieve the answer is either b or c, but i'm leaning more towards c.hope my answer has you : )