A wavelength is the distance between 2 successive waves (sound waves, ocean waves, or any other wave.)
Short wavelength
There is no longest wavelength for photons. It can be arbitrarily long.
It depends on what you consider high frequency and long wavelength. However, as frequency increases, wavelength decreases and vice versa. In fact, frequency is inversely proportional to wavelength.
Long
I looked it up in my physics text book and it says that the wavelength is too long to be seen by the human eye.
23
The wavelength of infrared light is too long for humans to see.
How long is your co-ax???
Scattering of light
The color of visible light with the longest wavelength is red; the color with the shortest is violet. So "ROY G. BIV" lists the colors from long to short wavelength. Just to confuse you, we'll also mention that it lists them from lowest to highest frequency.
A wavelength that measures 10^2 would be 100 meters long.
Long