AQA ยท A level Physics

Warm dense matter and X-ray modelling challenge

Can you get 100%? Use an XFEL experiment on compressed aluminium to test standard form, percentage difference, photons and model evaluation.

Read about the warm dense matter experiment

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Question

9 marks

Answer all parts. Show your working and give units where appropriate.

1(a)

The aluminium is compressed to a pressure of 50 GPa. Express this pressure in pascals in standard form.

[2 marks]

1(b)

A simplified model predicts a collective electron-oscillation energy of 80 eV, but the measured value is 60 eV. The 20 eV difference appears as a difference in scattered X-ray photon energy. Calculate the corresponding photon-frequency difference. Use 1 eV = 1.60 x 10^-19 J and h = 6.63 x 10^-34 J s.

[3 marks]

1(c)

An X-ray photon transfers energy and momentum to a coordinated oscillation of electron density called a plasmon. The scattered X-ray has a different energy. Explain how the measurement tests the electron model and why the disordered ion positions may need to be included.

[4 marks]

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