Text 1 

The form of energy that illuminates our world is called light. It usually comes from hot objects, like the sun or fire, but it is also produced by electricity and some chemical reactions. Light is the only part of the electromagnetic spectrum (which includes microwaves, ultraviolet rays, and X-rays) that is visible to the human eye. It travels at 186,000 miles (300,000 km) per second, and nothing can travel faster. Like other forms of energy, light travels in waves, but it can also travel in packets of energy called quanta. This enables it to travel through a vacuum.

Text 2 

Quantum Theory explains the behavior of light and other forms of energy in the electromagnetic spectrum. Quantum theory explains how light behaves in some ways like waves, and in other ways like streams of particles, which are in fact packets of energy called a quantum (one packet is called a quantum). There are three instances, shown when light can be explained only in terms of quanta.

Text 3 

The word laser stands for «Light Amplification by Stimulated Emission of Radiation.» A laser is a device for converting ordinary light into and intense narrow beam. The laser passes an electric current through a material, which can be a solid, liquid, or gas. Some atoms of the material take in energy and give off quanta (packets of radiation). This causes other atoms to give off quanta. These bounce back and forth between mirrors and are fired out as light of a single wave length.

Text 4 

Rays of light, like all forms of energy that travel in waves, can be reflected. Light rays are reflected when they hit a shiny or silvered surface, such as a still pool of water or a mirror. Reflection involves two light rays: the incoming and the reflected, or outgoing, ray, which bounces off the reflecting surface. The two rays are at identical angles to the reflecting surface on either side of an imaginary line.

Text 5 

Refraction is a property of all types of energy that travel in waves, including light. Light waves normally travel in straight lines, but when they pass from one transparent material to another, they usually refract, or bend. Refraction occurs because light travels at different speeds in different materials. As light from a material with a low density, such as air, enters a material with a high density, such as water, its speed is reduced. This causes it to bend (except when it enters a material at a right angle).

Text 6 

The three primary colors of light are red, green, and blue. When you mix one primary color equally with another, a secondary color is formed. When you mix all three primary colors, you get white light. The way different colors of light combine is known as the additive process.