1. Isaac Newton 1643 - 1727

2. Light behaves like small particles - corpuscles Light travels in straight lines Reflect off opaque surfaces Penetrate transparent materials White light made of colors

3. Newton Problems with Reflecting Telescopes * Longer focal length harder to make * Chromatic Aberration

4. Newtonian Telescope

5. Light behaves like waves –1600s Christian Huygens Refraction & Reflection explained by wave theory of light Problem – can’t see around corners

6. By 1800 Light has component parts Light behaves as a particle

7. William Herschel 1738 – 1822 – Discovers Infra-red

8. 1801 Johann Wilhelm Ritter discovers Ultraviolet Light

9. –1827 Thomas Young and Augustin Fresnel Measures wavelength Observes interference of waves http://micro.magnet.fsu.edu/primer/java/interference/doubleslit/

10. 1820 Hans Christian Ørsted –Discovers relationship between electricity & magnetism –In 1802 Italian Gian Domenico Romagnosi had already announced this was ignored

11. 1845 Michael Faraday –Fields

12. Electric Fields Magnetic Fields

13. Michael Faraday Light affected by a magnetic field

14. 1873 James Clerk Maxwell – finds the mathematical relationship between electric fields and magnetic fields

15. Electromagnetic Waves 1.Visible light is EM energy 2.There should be other EM frequencies

16. 1889 Heinrich Hertz –Produces small electromagnetic waves that have properties of light –Produces Radio Waves or “Hertzian waves”

17. 1895 Wilhelm Roentgen –Discovers X - Rays

18. By 1900 Light, Radio and X-rays are Electromagnetic Waves

19. 1930 Microwaves Explored –WW II pushes research –Commercial Research after war

20. 1914 Gamma Rays Included –Henri Becquerel “Becquerel’s Rays” Radioactivity –Marie & Pierre Curie discover new elements Polonium & Radium –Paul Villard finds stronger rays emitted by radium –1914 Ernest Rutherford measures wavelength

21. Early 1900s We know “light” is a form of electromagnetic radiation There are many different “kinds” of light or electromagnetic radiation

25. Think of Light as a stream of particles Each particle has a certain amount of energy

26. Is Light a Wave or a Particle? Wave Particle Duality