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6 (a) Interference of waves from two sources can only be observed when the waves are coherent - OCR - A-Level Physics A - Question 6 - 2010 - Paper 1
Question 6
6 (a) Interference of waves from two sources can only be observed when the waves are coherent. Explain the meaning of (i) interference. When two waves meet, they ... show full transcript
Worked Solution & Example Answer:6 (a) Interference of waves from two sources can only be observed when the waves are coherent - OCR - A-Level Physics A - Question 6 - 2010 - Paper 1
Step 1
Explain the meaning of (i) interference.
Answer
Interference occurs when two or more waves meet and combine at a point, leading to a variation in intensity and amplitude. This combination can produce areas of constructive interference, where wave peaks overlap, resulting in increased amplitude, and destructive interference, where a peak meets a trough, causing a decrease in amplitude. Overall, the resultant wave is a superposition of the individual waves.
Step 2
Explain the meaning of (ii) coherence.
Answer
Coherence is the property of waves indicating a constant phase difference between them over time. This means the two waves maintain a consistent relationship in terms of timing and phase alignment, which is crucial for the observation of interference patterns.
Step 3
Use the ideas of path difference or phase difference to explain how the interference pattern is formed.
Answer
The interference pattern is formed due to the path difference between the waves emanating from transmitters A and B. As the waves travel to point P, the distance traveled by each wave may differ, resulting in a phase difference. At points where the path difference is a multiple of the wavelength (e.g., 0, λ, 2λ), constructive interference occurs, leading to high intensity. Conversely, at points where the path difference is an odd multiple of half the wavelength (e.g., λ/2, 3λ/2), destructive interference occurs, leading to low intensity. This creates an alternating pattern of high and low intensity on the detector.