Our eyes are sensitive to a narrow range of electromagnetic waves known as visible light. Visible light has wavelengths ranging from approximately 400 to 700 nanometers, corresponding to the colors we perceive from violet to red.
The ability of our eyes to detect visible light is due to the presence of specialized light-sensitive cells called cones and rods in the retina. These cells contain photopigments that absorb photons of specific wavelengths within the visible light spectrum. When photons are absorbed, they trigger chemical reactions that generate electrical signals, which are then sent to the brain for visual interpretation.
However, electromagnetic waves with wavelengths outside the visible light spectrum, such as radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays, do not activate the photopigments in our cones and rods effectively. The energy carried by these waves is either too low (e.g., radio waves) or too high (e.g., X-rays and gamma rays) to be detected by the cells in our eyes.
Different types of electromagnetic waves interact with matter in different ways. For example, radio waves and microwaves pass through most objects with ease, while X-rays and gamma rays are highly penetrative and can ionize atoms and molecules, posing potential health risks.
Although we cannot see these non-visible electromagnetic waves directly, we have developed technologies that allow us to detect, measure, and use them for various purposes. For instance, radio waves are used for wireless communication, microwaves for cooking, and X-rays for medical imaging. These technologies rely on specialized devices that can detect and convert these waves into signals our eyes can perceive or instruments that can interpret and utilize the information carried by these waves.