Mathematical and Physical Journal
for High Schools
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# Problem P. 4233. (February 2010)

P. 4233. The inside of a half cylinder is silver-coated. The radius of the cylinder is R=6 cm. At a distance of h=4 cm from its symmetry axis there is a narrow beam of light. At what point does this beam of light focused?

(5 pont)

Deadline expired on March 10, 2010.

Sorry, the solution is available only in Hungarian. Google translation

Megoldás. A fókuszpont a visszavert nyaláb tengelyén van, a visszaverődési ponttól $\displaystyle f=\frac{1}{2}\sqrt{R^2-h^2}\approx 2{,}24$ cm távolságban.

### Statistics:

 44 students sent a solution. 5 points: Béres Bertold, Bodosi Eszter, Janosov Milán, Jéhn Zoltán, Kaposvári István, Réti Dávid, Tóth Bence Barnabás, Varju 105 Tamás. 4 points: Both Ambrus, Neumer Tamás, Para Attila, Patartics Bálint. 3 points: 2 students. 2 points: 13 students. 1 point: 14 students. 0 point: 3 students.

Problems in Physics of KöMaL, February 2010