Mathematical and Physical Journal
for High Schools
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# Problem P. 4812. (February 2016)

P. 4812. There is a point-like light source $\displaystyle T$ on the principal axis of a converging lens at a distance of $\displaystyle d$ from the lens. There is a plane mirror on the other side of the lens opposite to the lens. The mirror is perpendicular to the principal axis.

$\displaystyle a)$ If the mirror is moved along the principal axis, then the image of the light source, formed by the system, always coincides with the light source. How can this happen?

$\displaystyle b)$ The distance between the light source and the lens is doubled. Where should the mirror be placed in order that parallel light rays leave the system.

(4 pont)

Deadline expired on March 10, 2016.

### Statistics:

 46 students sent a solution. 4 points: Asztalos Bogdán, Bartók Imre, Csire Roland, Csuha Boglárka, Debreczeni Tibor, Elek Péter, Gémes Antal, Horváth 914 Bálint, Kasza Bence, Kormányos Hanna Rebeka, Kovács Péter Tamás, Körmöczi Dávid, Krasznai Anna, Mándoki László, Marozsák Tóbiás , Molnár Mátyás, Nagy 555 Botond, Németh 777 Róbert, Németh Flóra Boróka, Páhoki Tamás, Pataki 245 Attila, Pázmán Előd, Póta Balázs, Pszota Máté, Radnai Bálint, Sal Kristóf, Sallai Krisztina, Simon Dániel Gábor, Szántó Benedek, Szepesi Zoltán, Szick Dániel, Tanner Martin, Tófalusi Ádám, Topa Lukács, Tóth 111 Máté , Tóth Bence, Török Péter, Varga-Umbrich Eszter, Veres Tamás, Wiandt Péter. 3 points: Osváth Botond, Simon 727 Máté. 2 points: 3 students. 0 point: 1 student.

Problems in Physics of KöMaL, February 2016