What is the definition of light in optics?

In optics, light is defined as electromagnetic radiation that can be perceived by the human eye. This encompasses a specific range of wavelengths within the electromagnetic spectrum, typically from around 400 nanometers (nm) to 700 nm, which corresponds to the colors visible to humans. This definition highlights the interaction between light and human perception, emphasizing that light is not just any form of electromagnetic radiation but specifically that which can be detected visually.

The focus on human perception distinguishes this definition from other forms of electromagnetic radiation, such as infrared or ultraviolet light, which exist outside the visible range and are not directly perceivable. This makes the definition particularly relevant in the context of optics, which involves the study of light and its behaviors, such as reflection, refraction, and dispersion.

In contrast, other options mention heat energy or sound waves, which are unrelated to the concept of light in optics. Heat energy is connected to thermal radiation, while sound waves pertain to mechanical vibrations in a medium, neither of which is applicable when discussing the nature of light in the context of visual perception.