light theory

• Historical Milestones Development of Light Theory
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• 2. Historical Development Isaac Newton – Particle Theory & Prism Christiaan Huygens – Wave Theory Thomas Young – Double-Slit Experiment James Maxwell – Electromagnetic Theory Heinrich Hertz – Radiowaves & Wireless Experiment William Roentgen – X-rays Max Planck – Radiation Theory Albert Einstein – Photo Model
• 3. Isaac Newton (1642-1727)  Particle Model of Light (1671)  Light rays is comprised of a stream of massless particles
• 4. Particle Model of Light (1671) Explains straight-line propagation of light:  Follows laws of reflection and refraction Explains colours of light:  White light contains different colour particles  Prism sorts the different particles of light http://www.sciencephoto.com/image/227396/530wm/H4140126-Newton_s_optics-SPL.jpg
• 5. Christiaan Huygens (1629-1695) Wave Theory (1678) Light is a wave that can transfer energy without transferring matter Light waves have varying wavelengths, frequencies, speeds and amplitude
• 6. Wave Theory (1678) Follows laws of reflection and refraction Explains diffraction: the effect of waves when encountering an obstacle  Constructive and destructive interference http://www.sciencephoto.com/image/2511/530wm/A1800254-Water_waves-SPL.jpg
• 7. Wave Theory  Waves are additive: constructive interference  Example: waves in the ocean are bigger when more than one wave moves together  Waves are subtractive: destructive interference  A wave that meets a trough of equal amplitude cancel each other out (net zero amplitude)http://upload.wikimedia.org/wikipedia/commons/3/33/Doubleslit3Dspectrum.gif http://en.wikipedia.org/wiki/File:Doubleslit.svg
• 8. Thomas Young (1773 – 1829)  Wave Theory of Light  Proved that light propagates as a wave  Performed an experiment that demonstrated interference patterns in light that followed the rules of diffraction seen in water waves
• 9. A coherent light is shone through a thin plate