1. L IGHT E NERGY Unit 4

2. L IGHT E NERGY Light is a form of energy that can be seen. Light travels at a speed of about 300,000 kilometers per second (186,282 miles per second.) Light travels in a straight line. Light can pass through water, glass, air, or other mediums. When light passes through a medium, the direction can change and the speed can slow down. If light passes through a dark material or thick substance, the speed of light is much slower, and some of the light waves are absorbed.

3. R EFLECTION Reflection is light energy that bounces off the surface of an opaque object. The angle of reflection is the angle at which light is reflected by a surface. An example of an object that can reflect light is a mirror. When light strikes a mirror, it bounces off and changes direction. Beams of sunlight can be seen when light is reflected off water particles. This often occurs on foggy days. Although mirrors and shiny surfaces reflect light best, other objects, such as computer screens and windows, reflect light.

4. R EFRACTION Refraction is the bending of light rays as they pass from one substance to another. Refraction occurs when light hits an object, and its speed is changed. Refraction causes objects to look distorted. When a straw is placed in water, it appears to be broken because light travels at different speeds through air and water. Other objects may appear larger or smaller. Some objects can reflect and refract. For example, light can reflect off the surface of a pool. In the same pool, a coin at the bottom may appear to be in a different location.