488.0 nm (wavelength of argon laser)
3 Answers

Wavelength of EM waves is related to the freqency by the following formula:
c = (lambda) x f
where c is the speed of light (3×10^8 ms1), the greek letter lambda is wavelenth (in metres) and f is frequency (in hertz)
so the frequency of a wave with wavelength 488×10^9 metres is 6.1475×10^16 Hz, approximately 6.15×10^16 Hertz

you dont really need that equation because the equation you were using is to calculate energy in joules. The equation you should use is c = ( wavelength x frequency) (3.0 x 10^ 8 m/s) = ( 337.1) ( frequency) —>> divide most side by 337.1 8.9 x 10^5 Hz or ( 1/s) = frequency Im supposing the wavelength unit is in meters cuz you didnt specify Plus you can check you answer by plug it back into the equation and see if it gives you any of values you started with

6.15 x 1014 s¯1