Presentation on theme: "CH 1: THE NATURE OF LIGHT. Wave – Particle Duality Light exhibits both wave and particle characteristics. Both characteristics are present at all times,"— Presentation transcript:
Wave – Particle Duality Light exhibits both wave and particle characteristics. Both characteristics are present at all times, but certain characteristics are more prevalent in certain circumstances. Wave Nature Propagation Interference Diffraction Particle Nature Exchanging energy with matter Compton Scattering Photoelectric Effect Electromagnetic Spectrum: Radio Waves – Telecommunications (radio, TV) AM (188 m - 556 m) FM (2.78 m - 3.41 m) Microwaves (1 mm – 30 cm) Cooking, Radar, Telecommunications, Spectroscopy Infrared (IR) (770 nm – 1 mm) Night Vision, Infrared Photography Visible (770 nm – 380 nm) Ultraviolet (UV) UV-A (380 nm – 315 nm) Skin Aging and Skin Cancer UV-B (315 nm – 280 nm) Sunburn and Skin Cancer UV-C (280 nm – 10 nm) Ozone Formation X-Rays (10 nm – 10 -4 nm) Medical Diagnostics, Crystal Structure Gamma Rays (0.1 nm – 10 -14 nm) Medical Diagnostics
Reflection: Reflection is the simplest method for changing the direction of light. Reflection – Light incident on a boundary between two mediums is absorbed and reemitted back into the original medium. Incident Ray Reflected Ray Surface Normal ii rr When light is reflected from a surface it takes the path of least time. This will correspond to the path of least distance since the speed is constant. The path of least distance requires that the angle of incident be equal to the angle of reflection. Law of Reflection i – incident angle r – reflected angle The angle is always measured relative to the surface normal!! The law of reflection holds true for all electromagnetic waves. There are two main categories of reflection. Specular reflection – light reflected off of a smooth surface. Reflected rays will all be parallel. Diffuse reflection – light reflected off of a rough surface. The reflected rays are in a variety of directions Smooth surface – irregularities are smaller than the wavelength of the light.