A-Level AQA Physics Stationary Waves: This question is about an experi

Question

This question is about an experiment to measure the wavelength of microwaves.

A microwave transmitter T and a receiver R are arranged on a line marked on the bench.

A metal sheet M is placed on the marked line perpendicular to the bench surface.
The circuit connected to T and the ammeter connected to R are only shown in the plan view.

Figure 1 shows side and plan views of the arrangement.

The distance $d$ between T and R is recorded.

T is switched on and the output from T is adjusted so a reading is produced on the ammeter as shown in Figure 2.

M is kept parallel to the marked line and moved slowly away as shown in Figure 3.

The reading decreases to a minimum reading which is not zero.
The perpendicular distance $x$ between the marked line and M is recorded.

State the phase difference between the sets of waves superposing at R when the ammeter reading is a minimum.
Give a suitable unit with your answer.

Explain why the minimum reading is not zero when the distance $x$ is measured.

When M is moved further away the reading increases to a maximum then decreases to a minimum.

At the first minimum position, a student labels the maximum $n = 1$ and records the value of $x$.
Several positions of maxima and minima are produced.

Describe a procedure that the student could use to make sure that M is parallel to the marked line before measuring each value of $x$. 
You may wish to include a sketch with your answer.

It can be shown that 
$$nrac{	au}{2} = rac{	ext{sqrt}(x^2 + y^2) - y}{y}$$
where $	au$ is the wavelength of the microwaves and $y$ is the distance defined in Figure 1.

The student plots the graph shown in Figure 4.

The student estimates the uncertainty in each value of $$rac{	ext{sqrt}(x^2 + y^2)}{y}$$ to be 0.025 m and adds error bars to the graph.

Determine 
- the maximum gradient $G_{max}$ of a line that passes through all the error bars
- the minimum gradient $G_{min}$ of a line that passes through all the error bars.

Determine $	au$ using your results for $G_{max}$ and $G_{min}$.

Determine the percentage uncertainty in your result for $	au$.

Explain how the graph in Figure 4 can be used to obtain the value of $y$.
You are not required to determine $y$.

Suppose that the data for $n = 13$ had not been plotted on Figure 4.
Add a tick (\u2713) in each row of Table 1 to identify the effect, if any, on the results you would obtain for $G_{max}$, $G_{min}$, $	au$ and $y$.

This question is about an experiment to measure the wavelength of microwaves - AQA - A-Level Physics - Question 1 - 2017 - Paper 3

Worked Solution & Example Answer:This question is about an experiment to measure the wavelength of microwaves - AQA - A-Level Physics - Question 1 - 2017 - Paper 3

State the phase difference between the sets of waves superposing at R when the ammeter reading is a minimum.

Explain why the minimum reading is not zero when the distance x is measured.

Describe a procedure that the student could use to make sure that M is parallel to the marked line before measuring each value of x.

Determine the maximum gradient Gmax of a line that passes through all the error bars.

Determine the minimum gradient Gmin of a line that passes through all the error bars.

Determine τ using your results for Gmax and Gmin.

Determine the percentage uncertainty in your result for τ.

Explain how the graph in Figure 4 can be used to obtain the value of y.

Add a tick (✓) in each row of Table 1.

Join the A-Level students using SimpleStudy...