Physics problem of the month

This is the fun part of my page.
Each month a hard physics problem made by Prof. Ant is posted and every passionate physicist - from student to senior scientist - is invited to puzzle over it.
You can take yourself as much time as you need and may use any resource you like - the problems are not meant to be solved in one afternoon.
The topics are chosen from many different areas and require knowledge in classical and quantum mechanics, electrodynamics, statistical physics, relativity and condensed matter theory. 
ENJOY!

This is the problem of the month of April 2022. Past problems and their solutions can be found here. The next problem will be published in May 2022.

The exercises have been checked carefully.

However, if you come across some mistakes or inaccuracies, please let me know!

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