What is indicated by the term 'ray diagram'?

The term 'ray diagram' refers to a specific type of diagram that visually represents the path that light rays take as they travel through different media, interact with mirrors, or pass through lenses. This representation is essential for understanding how light behaves when it encounters various optical elements, such as reflections and refractions.

Ray diagrams are particularly useful in the study of optics because they allow students and scientists to predict the behavior of light in a systematic way. For example, in studying lenses, ray diagrams illustrate how parallel rays of light converge or diverge depending on the type of lens, helping to understand concepts like focal length and image formation.

The other options relate to different fields: light intensity is measured through other means, sound travel is explored through wave diagrams, and electrical flow is depicted in circuit diagrams. Thus, the correct answer accurately captures the fundamental purpose of ray diagrams within the study of optics.