λ= V/f
but change it to represent the speed of light, c
λ= c/f
c = 3.00 x 10^8 m/s
Plug in your given info and solve for λ(wavelength)
λ= 3.00 x 10^8 m/s / 7.5 x 10^14 Hz
(3.00 x 10^8) / (7.5 x 10^14) = 300,000,000 / 750,000,000,000,000 = 0.0000004
Hope this helps :)
