A ray of light is a conceptual representation of the path along which light travels. It is used to simplify the understanding of light propagation. In reality, light consists of electromagnetic waves, and its behavior is more accurately described by wave optics. However, the concept of a ray of light helps in understanding the basic principles of light propagation.
A ray of light is often represented as a straight line with an arrow indicating the direction of travel. It is used to illustrate how light interacts with objects, such as reflection, refraction, and diffraction. Rays of light can be used to determine the direction in which light is incident, reflected, or refracted at the boundaries between different materials.
Regarding the size of a ray of light, it is important to note that light itself does not have a physical size. Light is made up of photons, which are elementary particles without volume. Photons are considered point-like particles with zero size. However, when we refer to the "size" of light, we usually mean the beam diameter or the cross-sectional area of the light beam, which can vary depending on the light source and how it is manipulated or focused.
In summary, a ray of light is a simplified representation of the path along which light travels, and it does not have a physical size. The size of light is generally discussed in terms of the beam diameter or the cross-sectional area of the light beam.