Presentation on theme: "Diffraction and Interference of Light Chapter 19."— Presentation transcript:
Diffraction and Interference of Light Chapter 19
19.1 When Light Waves Interfere Grimaldi found that edges in shadows are not perfectly sharp. Diffraction- bending of waves around a barrier Huygens – all points of a wave front of light could be thought of as new sources of smaller waves. Fig
Young – dev. experiment to explain how light acts as a wave Produced pattern of light and dark bands, interference fringes Constructive & destructive interference Fig 19 –2 445 Monochromatic- one color –wide central band Coherent waves – waves are in phase.
White light – central band is white, other bands depend on Fig Young also measured of light. Fig = xd/L x - distance from central to next band, d - distance between slits and L - distance from slit to screen. Ex Prob 448
Single slit – bright central band with dimmer bands on each side Fig 19-5 & x = L/w x - distance from central to next band, w – width of slit, and L - distance from slit to screen. Fig Prac Pr 451
19.2 Applications of Diffraction Colors on butterfly wings and beetles are produced by diffraction. Diffraction grating – transmits or reflects light & forms an interference pattern like double slit.
Holography – produces a 3-D image that is difficult to copy. P 453
Spectroscope – used to measure Fig & Fig = xd/L = d sin Diffraction limits the ability of a lens to distinguish two closely spaced objects. Rayleigh criterion – if central band of one star falls on central band of the other can be resolved. Can be reduced by increasing size of lens.