rays
25.1 The Ray Aspect of Light There are three ways in which light can travel from a source to another location. See Figure 25.3. It can come directly from the source through empty space, such as from the Sun to Earth. Or light can travel through various media, such as air and glass, to the person. Light can also arrive after being reflected, such as by a mirror. In all of these cases, light is modeled as traveling in straight lines called rays. Light may change direction when it encounters objects such as a mirror or in passing from one material to another such as in passing from air to glass , but it then continues in a straight line or as a ray. The word ray comes from mathematics and here means a straight line that originates at some point. It is acceptable to visualize light rays as laser rays or even science fiction depictions of ray guns . Ray The word ray comes from mathematics and here means a straight line that originates at some point.