Lesson 2: The Interaction of Light and Matter – We learned that reflection occurs when light waves bounce off the surface of a material. In transmission most light waves travel through an object. When absorption occurs light energy is converted into other forms of energy. A material is transparent if it allows almost all light that strikes it to pass through and forms a clear image. A material is translucent if it allows most of the light that strikes it to pass through but forms a blurry image. A material is opaque if light does not pass through it. Next we learned that the law of reflection states that the angle of incidence always equals the angle of reflection. The normal to the surface is a line that is perpendicular to the surface. A light source is an object that emits light. Light spreads out in all directions from a light source. A narrow beam of light that travels in a straight line is called a light ray. Many objects reflect light. Reflected light waves travel from an object to your eyes allowing you to see the object. Dust scatters light. Scattering occurs when light waves traveling from one direction are made to travel in many directions. When light waves travel from one material into another the light waves change speed and direction. Refraction is the change in direction of light waves when they travel from one material to another material. The greater the change in speed, the more the light wave changes direction.
Discussion Question:
Think of three different materials – one transparent, one translucent, and one opaque. What happens when light comes in contact with each material?
An example of a transparent material is clear glass; when light comes in contact with glass it transmits the light waves and objects can be seen clearly through the glass. An example of a translucent material is glass brick; it transmits light waves but objects cannot be seen clearly through it. An example of an opaque material is black cloth; light waves cannot travel through the material.