Two beams of coherent light start out at the same point in phase and travel different paths to arrive at point P. If the

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Two beams of coherent light start out at the same point in phaseand travel different paths to arrive at point P. If the maximumconstructive interference is to occur at point P, the two beamsmust travel paths that differ by
A. a whole number of wavelengths.
B. an odd number of half-wavelengths.
C. a whole number of half-wavelengths.
D. None of the above.
4. A single-slit diffraction pattern is formed on a distantscreen. Assuming the angles involved are small, by what factor willthe width of the central bright spot on the screen change if theslit width is halved?
A. It will be cut to one-quarter its original size.
B. It will be cut in half.
C. It will double.
D. It will become four times as large.
E. It will become eight times as large.