Discovering Light

What is light? Scientists have asked this question for centuries.

Early scientists wondered: How do we see? How does light move? How fast is light? How do we see?

• How do we see? Explaining how we see in three dimensions was difficult.
• How does light move? Pinhole cameras show how light rays travel in straight lines.
• How does light move? Lenses show how light rays can bend.
• How fast is light? For a long time light was too fast to measure.

James Clerk Maxwell discovered visible and invisible waves of light.

• Light was described by Maxwell's theory of electricity and magnetism.
• This theory predicted invisible light waves, like x-rays and radio waves.
• This theory also explained the different colours of sunlight.
• Maxwell showed how the colours mix back together.

Is light a wave or a particle? Light is both waves and particles!

• Both theories describe some situations easily.
• The phenomenon of interference shows the waves of light.
• Another phenomenon, the photoelectric effect, shows the particles of light.
• Lasers and holograms use the weird quantum behaviour of photons of light.