1. Light
What is Light?

2. Three Ideas about what Light Is
Rays or Streamers
People commonly think of light as a ray
Socrates and Plato thought light to be “filaments” that went from the eye to the object
Particles
Democritus and other Greeks thought of light as a stream of particles. Modern scientists call light particles Photons
Waves
Newton discovered that light behaved like a wave

3. Newton on Light
Isaac Newton did experiments in which light formed interference and diffraction patterns just like a wave.
Still he preferred the particle theory
Later other scientists built on his experiments and found that light was two transverse waves:
One Magnetic, One Electric moving together.
Light is an “Electro-Magnetic Wave”

4. Einstein on Light
In 1905 Albert Einstein discovered how light was formed. He called it the photo-electric effect.
Light is created as little particles of energy called photons
So which is right?
Particle or Wave?

5. Wave-Particle Duality
Both Are!
Most scientists now believe that light has a dual nature
Light is a…
Wave and a Particle
It is called
Wave-Particle Duality