Light

Light

Luminous Objects
1. Sources of Light
2. Visible because produce light
3. Examples
  1. Torch
  2. Sun
  3. Firefly
Non-luminous objects
1. Examples
  1. Glass
  2. Moon
  3. Reflective Jacket
2. Only visible by reflectiong light
Light travels in every direction from a source
Lasers
1. Special light source
2. produces ray of light= in one direction
Speed of Light
1. In vacuum
  1. c=300 000 km/s
2. In air slightly less
3. In more denser objects much less
Shadows
1. formed when....
  1. light travels in straight line
  2. when light is partially blocked by an opaque object
2. Types of Object
  1. Transparent eg glass
    1. light passes through
  2. Translucent eg paper
    1. light is scattered
  3. Opaque object eg metal
    1. light absorbed leaving shadow
  4. look in book if need diagrams
Point sources
1. light from very small point
2. produces sharp shadow
3. look in book if diagram needed
Umbras + Penumbras
1. extended source of light (eg sun, striplight)
  1. produces 2 types of shadow behind an opaque object
    1. umbra
      1. 100% of source is blocked
      2. Dark shadow
    2. penumbra
      1. 0%-100% of source is blocked
      2. Fuzzy shadow
      3. look in book for diagram if needed

Resource summary

	Created by InSaNe X bEzErK almost 10 years ago