Physics Review Question Unit: waves Year: 1996 Question#: 42 Question: the diagram represents shallow water waves of wavelength x passing through two small openings, A and B, in a barrier. Compared to the length of path BP, the length of path AP is (1 ) 1 longer (2 ) 2 longer (3 ) 1/2 longer (4 ) the same What is this question really asking? Explanation by: Becky G [ Return to question menu ] Answer 1 1 longer INCORRECT According to the diagram a peak is lining up with a trough at point P, forming destructive interference. The only way a wave from one slit could create destructive interference with the wave from another slit is if the two paths differ by an odd number of half wavelengths. The half a wave extra causes peaks to line up with troughs. return to top Answer 2 2 longer INCORRECT According to the diagram a peak is lining up with a trough at point P, forming destructive interference. The only way a wave from one slit could create destructive interference with the wave from another slit is if the two paths differ by an odd number of half wavelengths. The half a wave extra causes peaks to line up with troughs. return to top Answer 3 1/2 longer CORRECT According to the diagram a peak is lining up with a trough at point P, forming destructive interference. The only way a wave from one slit could create destructive interference with the wave from another slit is if the two paths differ by an odd number of half wavelengths. The half a wave extra causes peaks to line up with troughs. Other acceptable answers could have been 3/2 or 5/2 of a wavelength if they were offered. return to top Answer 4 the same INCORRECT The lengths are not the same or the point P would be centered between the two points A and B. According to the diagram a peak is lining up with a trough at point P, forming destructive interference. The only way a wave from one slit could create destructive interference with the wave from another slit is if the two paths differ by an odd number of half wavelengths. The half a wave extra causes peaks to line up with troughs. return to top What's this question really asking? Can you interpret a double slit diffraction diagram and determine wher constructive and destructive interference occur? How do the two path lengths differ if you have destructive interference? return to top |
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