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
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Answer 1
1
longerINCORRECT
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
longerINCORRECT
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
longerCORRECT
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
