Mathematical and Physical Journal
for High Schools
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# Problem P. 4702. (January 2015)

P. 4702. Four concrete cubes, which are made of different material, and which all have the side of 10 cm are placed next to each other as shown in the figure. They are illuminated'' by a beam of $\displaystyle {}^{60}$Co gamma-ray, from four different positions, (S1, S2, S3 and S4) one after the other. Opposite to the gamma source behind the cubes there are four detectors (D1, D2, D3 and D4). The first three measurements shows that the concrete cubes decrease the intensity of the radiation by 86.76, 71.94 and 84.25 percent of the original value, respectively.

$\displaystyle a)$ What is the intensity of the radiation measured by the fourth detector, expressed in the percentage value of the intensity of the original radiation?

$\displaystyle b)$ The thickness of the halving-layer'' of the first cube is 6 cm. What is this value for the other cubes (which is characteristic of the material of the cube)?

(5 pont)

Deadline expired on March 10, 2015.

### Statistics:

 42 students sent a solution. 5 points: Balogh Menyhért, Bartók Imre, Bencsik Bálint, Berta Dénes, Blum Balázs, Bugár 123 Dávid, Büki Máté, Csathó Botond, Csire Roland, Fekete Panna, Forrai Botond, Gróf Tamás, Holczer András, Iván Balázs, Kaposvári Péter, Kasza Bence, Kovács Péter Tamás, Marosvári Kristóf, Marozsák Tóbiás , Németh Flóra Boróka, Olosz Balázs, Öreg Botond, Páhoki Tamás, Pázmán Előd, Pszota Máté, Radnai Bálint, Sal Kristóf, Szántó Benedek, Szentivánszki Soma , Tanner Martin, Trócsányi Péter, Varju Ákos, Wiandt Péter. 4 points: Asztalos Bogdán. 3 points: 2 students. 2 points: 1 student. 1 point: 4 students. 0 point: 1 student.

Problems in Physics of KöMaL, January 2015