1. 9.4 Light as a Wave or a Particle?

2. Time Frame for Newton/Huygen Newton (1643-1727) Born in England Huygen (1629 –1695) Born in Holland

3. What is the basis of each model/theory: Newton: _____________________ Huygens:______________________

4. Comparison Explanation/DescriptionExplained Well by the Theory? Rectilinear Propagation Diffraction Reflection Refraction Partial Reflection- Partial Refraction Dispersion Explanation/ Description Explained Well by the Newton’s Theory? Explained well by Huygens’ Theory? Rectilinear Propagation Diffraction Reflection Refraction Partial Reflection- Partial Refraction Dispersion

5. Comparison… Explanation/DescriptionExplained Well by the Theory? Rectilinear Propagation Diffraction Reflection Refraction Partial Reflection- Partial Refraction Explanation/ Description Explained Well by the Newton’s Theory? Explained well by Huygens’ Theory? Reflection- Light is absorbed fully on black surfaces yet particles reflect off any surface

6. In summary, Huygens’wave theory explained many of the properties of light, including reflection, refraction, partial reflection– partial refraction, diffraction, dispersion, and rectilinear propagation. The wave theory was more valid at that time than Newton’s corpuscular theory, but because of Newton’s reputation in other areas of physics, the corpuscular theory would dominate for 100 years, …until Thomas Young provided new and definitive evidence in 1807.

7. Read Section 9.5 1.What evidence did Thomas Young give to support the theory that light is a wave?