The correct answer is option 4 - light. The visible portion of the electromagnetic spectrum refers to the range of wavelengths of electromagnetic radiation that can be detected by the human eye. This range of wavelengths is approximately between 400 to 700 nanometers. It is important to note that the electromagnetic spectrum is divided into various regions such as radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays, each with different wavelengths and properties.

Option 1 - Infrared: Infrared radiation has longer wavelengths than visible light and is not part of the visible portion of the electromagnetic spectrum. It is commonly used in applications like thermal imaging and remote controls.

Option 2 - Radiowave: Radiowaves have even longer wavelengths than infrared and are also not part of the visible portion of the spectrum. They are often used for communication purposes, such as radio and television broadcasting.

Option 3 - Microwave: Microwaves have shorter wavelengths than radiowaves but are still not within the visible range. They are commonly used in microwave ovens and wireless communication.

Therefore, the correct answer is option 4 - light, as it represents the visible portion of the electromagnetic spectrum.