Light and Matter

1. Light and Matter

2. Ray Model of Light • In the Ray model of Light, light is represented as straight lines called rays which show the direction light travels. • Ray diagrams are drawing s that show the path that light takes after it leaves its source. • Each ray ends with an arrow to indicate the direction of travel. • The more rays that reach your eyes, the brighter the object appears.

4. Ray diagrams are used to describe what happens when light strikes an object. • Light travels in straight lines until it hits something. Some materials let light pass through, others absorb light, and others reflect light

5. Materials are classified according to the way they transmit. • Transparent – materials such as glass transmit light freely. This is why you can see clearly through a window. • Translucent – materials transmit some light but not enough to see through the material clearly. Ex. A frosted window. • Opaque – objects that absorb and reflect light but do not transmit it.

7. Shadows • Ray diagrams help explain the size and location of shadows and why some are sharp and others fuzzy. • A shadow occurs when an opaque object blocks the direct light from a light source. • A ray diagram illustrates how the size of a shadow depends on the size of the object and distance from the light source.

9. A small light source casts shadows that are sharp and well defined. The wider the light source, the more blurred the shadow.

10. Umbra – is the part of the shadow in which all light rays from the light source are blocked • Prenumbra – is the area of partial shadow from a non- point light source

11. Light Reflection You can see objects all around you because light reflects off surfaces. Incoming rays all travel in same direction and are parallel. Regular Reflection – light rays strike smooth surface and reflect in same direction parallel Diffuse Reflection – occurs when light rays reflect off a rough or uneven surface