It is accurate to say that the electromagnetic wave that humans can directly sense is visible light. The reason for this is that the human eye is specifically sensitive to a narrow range of wavelengths within the electromagnetic spectrum, which we perceive as colors.
Visible light encompasses wavelengths that range from approximately 400 nanometers (violet) to 700 nanometers (red). This portion of the electromagnetic spectrum falls between the shorter wavelengths of ultraviolet (UV) radiation and the longer wavelengths of infrared radiation.
The human eye contains specialized cells called photoreceptors, specifically cones and rods, located in the retina. Cones are responsible for color vision and work best in bright light conditions. They are sensitive to three primary colors: red, green, and blue. Through the combination of responses from these cones, our brains interpret and perceive different colors. On the other hand, rods are more sensitive to low-light conditions and do not provide color perception.
When visible light enters the eye, it is absorbed by these photoreceptors, and the brain processes the signals received from them to create our visual experience of the world in color.
While humans cannot directly sense other parts of the electromagnetic spectrum (such as radio waves, microwaves, X-rays, or gamma rays) with their eyes alone, we have developed technology that allows us to detect and utilize these other wavelengths for various applications, like radio communication, medical imaging, and more. Nonetheless, it is essential to recognize that our direct visual perception is limited to the visible light spectrum.