Diffraction Chapters 31

Wave Motion Waves propagate in all directions without barriers

Wave Fronts Line that represents waves that are all in phase, usually crests

Huygens Principle Every point on a propagating wave front serves as a source of a spherical secondary wavelet The corresponding spherical wavelets produce further wave fronts Basis for Diffraction, Reflection, Refraction

Huygens Principle

Huygens Principle

Huygens Principle First proposed explanation that light is a wave Newton later proposed that light is a particle

Diffraction Bending of waves around an obstacle or the edges of an opening Example: You can often hear people in the hallway without seeing them Shadows

Sound Diffraction

Diffraction

Diffraction

Diffraction Causes interference patterns a certain distance away from the source Bright and dark spots for light Loud and dead spots for sound Amount of diffraction is a measure of distance between consecutive bright spots

Young’s Double Slit Experiment Proof that light acts like a wave Light shining through 2 slit opening Bright and dark lines on screen

Diffraction Equation x = amount of diffraction λ = wavelength L = distance from opening to screen d = distance between slits d<<L

Examples Applet Laser Pointer

Path Difference

Path Difference For Maximum Constructive Interference the path difference is nλ For Maximum Destructive Interference, the path difference is (n +1/2)λ