Mathematical and Physical Journal
for High Schools
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# Problem P. 4159. (April 2009)

P. 4159. Two loud speakers, in the open air, emit the same frequency of sound in phase. One of them is at the origin of the coordinate system, and the other is at the point x1=0, y1=2.4 m. An observer is standing at the point x2=40 m, y2=0, and then along a straight line parallel to the y axis he walks to the direction of positive and negative y. While he is walking he finds that the intensity of sound decreases to both directions. What can the frequency of sound be? Along the same line can he find similar points?

(4 pont)

Deadline expired on May 11, 2009.

### Statistics:

 53 students sent a solution. 4 points: Barancsuk Lilla, Batki Bálint, Farkas Martin, Garaguly Gergő, Illés Dorottya, Jéhn Zoltán, Kiss 620 Gábor, Lászlóffy András, Lenger Dániel, Lőrincz Dóra, Maknics András, Mayer Martin János, Najbauer Eszter Éva, Neumer Tamás, Orosz Ákos, Papp Edina, Pázmán Koppány, Réti Dávid, Somogyi József, Szédelyi Roland, Török 999 Csaba, Varju 105 Tamás, Zelei Kristóf. 3 points: Benyó Krisztián, Boros Csanád Örs, Budafoki Richárd Gergely, Csányi Gergely, Egyed Zsombor, Farkas Márton, Földes Imre, Hartstein Máté, Hohmann Balázs, Jakab Dávid, Janosov Milán, Kaposvári István, Kardos Örs, Kovács 235 Gábor, Krämer Zsolt, Lovas Lia Izabella, Pálovics Péter, Paripás Viktor, Sass Zoltán, Tóth 222 Barnabás, Tóth Bence Barnabás, Török Lajos, Vécsi Áron, Wang Daqian. 1 point: 2 students. Unfair, not evaluated: 4 solutions.

Problems in Physics of KöMaL, April 2009