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 θmin = 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 θ1 = 1.22 λ d sin θ2 = 2.23 λ d sin θ3 = 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,

θmin = 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