That's impossible to say with the information provided in the question; Hertz is cycles per second and nanometers is a measure of length...
400 nanometers = 4.0 × 10-10 kilometers
7.5*
it is not knowlageable to me
The wavelength of light (400-700).
The answer is 5.0*1014 Hertz.
Most humans eyes are sensitive to wavelengths between about 400 nanometers and 700 nanometers
From the related links: between about 10 nanometers (most energetic Extreme Ultraviolet) to about 300 nanometers (least energetic Near Ultraviolet). Visible violet light is about 400 nanometers.
10 Tera hertz to 400 Tera hertz.
It is visible light.
The wavelength of the color violet is 450-400 nm, which can also be said as 450 to 400 nanometers.
Answer - meters or derivations of meters e.g micrometers, nanometers etc
Short answer: Very short More precise answer: 10 nanometers to 400 nanometers for one full wave (depending on how 'ultra' it is)