How Does Light Travel?

Light Moves in Waves

Light is a form of energy made of electromagnetic waves. Some of the waves you can see and some you cannot. The entire range of light is called the electromagnetic spectrum. The light you see is referred to as "visible light."

Light waves transport energy from its source to its surroundings. Usually, light travels very quickly. If unhindered, light waves can travel 300,000 km per second. Light traveling from the sun takes about 8.5 minutes to reach the earth. Light waves can be large or small. How big those waves are determines what type and color of light it is. Some waves are so small they actually appear as straight lines. However, light only moves in straight lines when it is not passing through a medium.

Light Waves Can Pass Through a Medium

Light waves can pass through air, water, glass, or other mediums. Passage through a medium can affect the speed and direction of the light waves. When it passes through a medium, such as water, it slows down. That is why a pencil will appear bent when placed in a glass of water. Only in spaces where there is no interference of its movement can light waves travel at maximum speed. When the waves are passing from the sun to the earth, the light is traveling as fast as it can go. This is faster than sound. When light waves pass through a dark, thick substance, such as a heavy cloth, the movement is slower. Some light waves may be absorbed by the medium. This is why not much light is reflected from the cloth when the waves bounce onto it.

Light Waves Can Reflect or Refract

Reflection occurs when light waves bounce off of something, such as a mirror. Light bounces off of the mirror and changes its direction. When you are looking at objects around you, light bounces off of the objects and back to your eyes. That is how you see the object. Light can also bounce off of particles in the air. Light bouncing off water particles in the air explains how beams of sunlight can be seen on a foggy day or how a rainbow appears on a rainy day. Light waves can also pass from one medium into another. When this happens, some of the light waves actually bend. Such is the case when the pencil is placed in the glass of water. This is called refraction. Refraction causes an object to look distorted.