In order to answer this question, we might use the formula in which we have frequency, wavelenght and the speed of light. This formula in order to find frequency will be written as it follows:
f = c/λ
where:
c = speed of light, which is 2.998*10^8 m/s
λ = wavelenght, which is 415 nm or 400*10^-9 meters
f = 2.998*10^8/400*10^-9
f = 7.49*10^14 Hz