Diffraction 101 Dick Furnstahl Department of Physics Ohio State - PowerPoint PPT Presentation

Diffraction 101 Dick Furnstahl Department of Physics Ohio State University Last revised: August 21, 2017

Outline Basic of diffraction and resolution in pictures

Diffraction 101 (review?)

Intensity as a Function of Angle Single-slit diffraction = ⇒ first minimum when sin θ min = λ/ a = ⇒ pattern widens as λ increases

Diffraction from a circular hole The diffraction pattern of a circular hole of diameter d is similar to that of a single slit of width a The bright spot in the middle is the Airy disk. It has about 85% of the power in the pattern Minima are at: sin θ 1 = 1 . 22 λ d sin θ 2 = 2 . 23 λ d sin θ 3 = 3 . 24 λ d What is the diffraction pattern from a solid disk? (Hint: Babinet)

Diffraction and resolution

Wavelength and resolution

Wavelength and resolution

Wavelength and resolution

Wavelength and resolution

Wavelength and resolution

Wavelength and resolution

Wavelength and resolution

Wavelength and resolution

Wavelength and resolution

Consequences For a slit of width a , θ min = sin − 1 ( λ/ a ) so if λ ≥ a , you don’t learn anything about the details of the slit

Quantum Mechanics and Resolving Power de Broglie relation: λ = h / p λ ≈ 10 − 10 m = ⇒ probe atoms λ ≈ 10 − 14 m = ⇒ probe nucleus λ ≈ 10 − 18 m = ⇒ probe quarks