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Explain how the apparatus can be used to demonstrate that the waves from T are vertically polarised - AQA - A-Level Physics - Question 2 - 2021 - Paper 1
Question 2
Explain how the apparatus can be used to demonstrate that the waves from T are vertically polarised. Figures 2a and 2b show T and R and two different positions of a... show full transcript
Worked Solution & Example Answer:Explain how the apparatus can be used to demonstrate that the waves from T are vertically polarised - AQA - A-Level Physics - Question 2 - 2021 - Paper 1
Step 1
Explain how the apparatus can be used to demonstrate that the waves from T are vertically polarised.
Answer
To demonstrate that the microwaves emitted from the transmitter T are vertically polarised, the apparatus uses a vertical aerial (R) at the receiver. When the aerial is aligned vertically, the received signal is at its maximum, confirming that it is detecting the vertically polarised waves. Conversely, if the aerial is rotated to a horizontal position, the signal dramatically decreases, indicating that the horizontal component of the waves is not being effectively detected. This behavior illustrates the plane of polarisation of the microwaves.
Step 2
Explain what happens to the signal detected by R as M is moved slowly towards X.
Answer
As M is moved slowly towards X, the signal detected by the receiver R shows a change in intensity. Initially, when M is at position in Figure 2a, R receives both direct and reflected microwaves. As M approaches X, the path length for the reflected waves changes, leading to variations in the phase difference between the direct and reflected signals. This results in constructive or destructive interference, causing fluctuations in the signal intensity received by R.
Step 3
Deduce whether this practical arrangement is suitable for a determination of a value for the wavelength.
Answer
This practical arrangement is not suitable for accurately determining the wavelength of the microwaves using the provided setup. The significant path differences, combined with the variations in signal reception due to interference effects caused by the reflection from M, could lead to ambiguities in measuring the wavelength. The condition for measuring wavelengths accurately in such setups is not met, especially considering the small wavelength relative to the distance involved.
Step 4
Suggest why Young's double-slit equation should not be used to determine the wavelength.
Answer
Young's double-slit equation assumes that the sources are coherent and that the path differences are negligible compared to the wavelength. In this setup, the separation between the slits (0.12 m) is significant compared to the wavelength (approximately 3 cm), leading to complications in maintaining coherence. Furthermore, the uses of a single receiver R and the reliance on interference patterns created by reflection rather than direct slit interference undermine the validity of directly applying Young's equation.