Unit: waves
Year: 1988 Question#: 43
Question: Maximum constructive interference between two waves of the same frequency could occur when their phase difference is
(1 )
(2 )
/2 (3 ) 3
/2(4 )
/4What is this question really asking?
Explanation by: Yui H.
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Answer 1
correct
Constructive interference is where peaks of one wave meet peaks of other waves. This answer is correct because if the wave of same frequency is moved one wavelength, the peaks of one wave will still meet peaks of another wave.
The diagram above shows pink wave moved one wavelength and still the peaks of red
wave meets the peaks of black wave.
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Answer 2
/2 incorrect
This answer is incorrect because if one wave is moved half a wave length, than peaks of one wave will meet troughs of another wave. When this happens peaks and troughs get cancelled out and get distructive interference.
The diagram above shows pink wave moved half a wave length and the peaks of black
wave meet with troughs of pink wave (distructive interference).
return to top Answer 3
3
/2incorrect
This answer is incorrect because if one wave is moved one and a half wave length, than peaks of one wave will meet troughs of another wave. When this happens peaks and troughs get cancelled out and get distructive interference.
The diagram above shows pink wave moved one and a half wave length and the peaks of
black wave meet with troughs of pink wave (distructive interference).
return to top Answer 4
/4incorrect
This answer is incorrect because if one wave is moved 1/4 of a wave length, the peaks of one wave won't meet the troughs of another wave, but the peaks will get cancelled out with lower part of another wave so its not maximum constructive interference.
The diagram above shows pink wave moved 1/4 of a wave length. The peaks of black
wave almost matches the peaks of pink wave, but it doesn't completely match so its
not maximum constructive interference.
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What is constructive interference? return to top
