Chapter 1. Understanding the Nature of Light

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Chapter 1. Understanding the Nature of Light

Light is the first thing we see when we open our eyes. But what is light? In general, light is an electromagnetic disturbance that travels through the fabric of space/time at 186,300 miles per second! Sound weird? Well, it gets weirder! Light is energy in its purest form. Light has both the properties of a wave and a particle, making it doubly vexing. Now, from our point of view here on Earth, we have lots of light during the day and limited light at night. The light we receive at night is mostly reflections from the moon and the sky. We perceive the sun as one big point of light giving off energy in all directions. Consider Figure 1.1, for example.

Figure 1.1. Directional light is limit ed and directed in a certain direction,where- as point light emits equally in all directions.

All planets are shaped like spheres, and each planet receives some of the sun's energy on one side (or hemisphere) at a time. This is how we perceive day and night. This limited amount of light directed on the lit hemisphere is called directional light . The sun that is emitting light equally in all directions is called a point light . But the sun is not the only source of light on the planet. We have other light sources, such as fire, white-hot filaments in light bulbs , and glowing gas in tubes.

Let's take a closer look at light's properties. According to physics, all light (or electromagnetic waves in general) is generated by the motion of charged particles, such as electrons (electrons have a negative charge). Light is an electromagnetic wave and visible light only accounts for a small portion of the bigger picturethe electromagnetic spectrum.

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