An electromagnetic wave with a frequency of 7.57 x 1014 Hz will have a wavelength of 3.96 x 10-7 m. t/f

Wavelength is equal to c/f = 3.96 x10^-7m. t/f where c is the speed of light and F is the frquency

f (frequency of the wave) = 7.57 x 10^14 Hz

c (speed of light is always=3 x10^8m/s

wavelenth is therefore={ (3x 10^8) / (7.57 x10^14) } = 0.396 x 10^-6=3.96 x 10^-7 (true)