Paper 4 Superposition of Waves Drills

Q1 Microwave stationary-wave measurement

A microwave transmitter is directed normally at a metal reflector. A detector is moved along the line between them. The positions of consecutive signal maxima are recorded.

Maximum number $n$	0	1	2	3	4	5
Position $x/\mathrm{cm}$	10.7	12.4	14.1	15.8	17.6	19.3

1. Explain how a stationary wave is formed. [2]
2. Plot $x$ against $n$ and draw a best-fit straight line. [5]

3. Use the gradient to determine the microwave wavelength. [3]
4. Determine the microwave frequency, taking wave speed as $3.00\times 10^8\mathrm{m}{\mathrm{s}}^{-1}$. [2]
5. Explain why using all maxima is preferable to using one adjacent pair. [2]
6. State two precautions for improving the measurement. [2]

Q2 Diffraction grating measurement

A student uses a grating and a spectrometer to measure wavelength.

1. State the measurements needed to use $d\sin \theta =n\lambda$. [2]
2. Explain why readings should be taken on both sides of the central maximum. [2]
3. State one source of systematic error. [1]