Calculate the Frequency of Light Whose Wavelength Is 4

Calculate the frequency of light whose wavelength is 4.2×10 ^{- 7} meters.

A) 6.2×10¹³ s ^{- 1}
B) 7.1×10¹⁴ s ^{- 1}
C) 8.3×10¹³ s ^{- 1}
D) 1.8×10¹⁴ s ^{- 1}
E) none of these