The correct answer to this question is color. Many images that are on the electromagnetic spectrum are able to be seen by the human eye. However, there are many other images that are unable to be seen from the human eye. The reason for this is the rays that are used on the spectrum.
It is also frequency and wavelengths that can impact how a person is able to see the spectrum. When we are able to see the light in wavelengths, our eyes are seeing colors. A person can see a number of different colors, including those colors that are infrared.
I believe that the answer shape could also be correct in this case, because your vision is seeing a shape, because of the wavelengths of the border's color.
Some images on the electromagnetic spectrum can be seen by the naked eye. However, most can’t. This has to do with the types of rays used as well as the frequency and wavelengths. Whenever we use our vision to view light in wavelengths, we are seeing colors.
The colors and objects that are visible by the naked eye on the electromagnetic spectrum include those that are near ultraviolet and near infrared. The near ultraviolet rays have a frequency of about 300 THz and they have a frequency of 1 wavelength.
The near infrared rays have a 3000 THz just like the near ultraviolet rays and they have either 1 or 10 wavelengths. Others that are not visible include ionizing radiation and microwaves.