THE PRACTICE STUDIO
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PRACTICE / Young double-slit experiment
Interference inside a diffraction envelope
Two identical slits of width a have centre separation d = 4a. Coherent monochromatic light illuminates them. Consider the far-field pattern near the centre.
How many interference-order positions lie strictly between the first single-slit diffraction minima, including the central order?
Organize the givens & assumptions
- Slit width: a
- Centre separation: d = 4a
- Count positions strictly inside the first diffraction minima
Identical uniformly illuminated slits with wavelength much smaller than a; Fraunhofer approximation. Count interference-order positions, not the slightly shifted extrema of the combined envelope.
- A
- B
- C
- D
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