PHYS 012A Lecture Notes - Lecture 28: The Joshua Files, Physical Optics, Optical Path Length
12 Jun 2018
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Wave Optics → Physical optics: includes interference, diffraction, and polarization
Interference
- In constructive interference the amplitude of the resultant wave is greater than that of either
individual wave.
- In destructive interference the amplitude of the resultant wave is less than that of either individual
wave.
- All interference associated with light waves arises when the electromagnetic fields that constitute
the individual waves combine.
Youg’s Double Slit Experiment: schematic
- The waves emerging from the slits had the same wave front and were in phase
Resulting Interference Pattern
- The light from the two slits forms a visible pattern on a screen; the pattern consists of a series of
bright and dark parallel bands called fringes
- Constructive interference occurs where a bright fringe occurs and destructive interference results
in a dark fringe.
Interference patterns
- Constructive: arrives in phase → bright fringe observed
o Start off the same and end the same; peak ends with peak
- Constructive: arrives in phase → lower wave travels one wavelength more, they go upward and
still end together
- Destructive: upper wave travels one half of a wavelength farther than the lower wave to reach a
point; the trough of the upper wave overlaps the crest of the lower wave -> dark fringe occurs.
Conditions for Interference:
- Sources must be coherent → maintain a constant phase with respect to each other
- Sources must be monochromatic → have a single wavelength
Diffraction:
- Wave bends around corners
- Spreads out through the splits
- The divergence of light from its initial line of travel is diffraction
Youg’s Doule-Slit Experiment: Geometry
- δ = r2 – r1 = d sin θ
- assumes the paths are parallel.
find more resources at oneclass.com
find more resources at oneclass.com
Interference Equations
Intensity Distribution, Electric Fields
Intensity Distribution, Phase Relationships
Intensity Distribution, Equation
Ex: move screen away, what happens to interference fringes? They increase
Ex: slit separation increases, what happens to interference fringes? They decrease
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Wave optics physical optics: includes interference, diffraction, and polarization. In constructive interference the amplitude of the resultant wave is greater than that of either individual wave. In destructive interference the amplitude of the resultant wave is less than that of either individual wave. All interference associated with light waves arises when the electromagnetic fields that constitute the individual waves combine. The waves emerging from the slits had the same wave front and were in phase. The light from the two slits forms a visible pattern on a screen; the pattern consists of a series of bright and dark parallel bands called fringes. Constructive interference occurs where a bright fringe occurs and destructive interference results in a dark fringe. Constructive: arrives in phase bright fringe observed: start off the same and end the same; peak ends with peak. Constructive: arrives in phase lower wave travels one wavelength more, they go upward and still end together.
