The portion of the visible spectrum that appears brightest to the human eye is approximately 560 nm in wavelength, which corresponds to yellow-green. what is the frequency of this light?

By definition we know that we can calculate the frequency of an electromagnetic wave by wavelength, using the following equation:

Where:

λ is the wavelength.

c is the speed of light

f is the frequency.

Then:

So:

We know that the speed of light is:

So:

Finally, the frequency is

i think its d if wrong im sorry