25.1 The Ray Aspect of Light

25.1 The Ray Aspect of Light

• Light can travel from a source to another location in three different ways.
• It can come directly from the source, such as from the Sun to Earth.
• Light can travel through various media to the person.
• Light can come from a mirror.
• Light is modeled as traveling in straight lines.
• Light may change direction when it encounters objects such as a mirror or when it passes from one material to another, but it continues in a straight line.
• Light rays can be visualized as laser rays or even science fiction depictions of ray guns.

• A straight line is what the word "ray" means.

• Light can travel from a source to another location.
• It can travel through media.

• It can look like a mirror.
• Light travels in straight lines when it interacts with large objects.

• Experiments and our own experiences show that when light interacts with objects several times as large as its wavelength, it travels in straight lines and acts like a ray.
• Its wave characteristics don't show up in those situations.
• Since the wavelength of light is less than a thousandth of a millimeter, it acts like a ray in a lot of situations.
• When light encounters a mirror, it acts like a ray, with only subtle wave characteristics, because we can't see it with our eyes.
• Ray characteristics will be the focus of this chapter.

• Since light moves in straight lines, changing directions when it interacts with materials, it is described by geometry and simple trigonometry.
• Light changes direction when it interacts with matter.
• For situations in which light bounces off matter and for situations in which light passes through matter, these are the laws of reflection and refraction.

• Geometric optics deals with the ray aspect of light.