The Behavior of Electromagnetic Radiation

"In a vacuum, all electromagnetic radiation travels at the same incredible speed of 3.00 × 10⁸ m/s, which is equal to 671 million miles per hour. This is one of the fundamental physical constants. It is referred to as the speed of light and is given the symbol *c*." "When light travels through a physical medium, its speed is always less than the speed of light... When light changes speeds at a boundary between media, it also changes direction. The greater the difference in speeds, the more the path of light bends." "Because ray 2 travels a greater distance, the two rays become *out of phase*... This causes **interference**, which reinforces the intensity of the wavelengths of light that create the bands of color." "Light with an electric field that vibrates in only one direction is called *polarized*." "A useful equation involving *c* is $c = f \lambda$ where *f* is frequency in Hz, and $\lambda$ is wavelength in meters." "The number of lumens per square meter is called **illuminance**, and is given in units of **lux** (lx)... $\text{illuminance} = \frac{P}{4 \pi r^2}$."