Mathematical and Physical Journal
for High Schools
Issued by the MATFUND Foundation
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# Problem P. 4612. (February 2014)

P. 4612. An object, which is at a distance of 30 cm from us, is observed through a lens. When the lens is close either to us or to the object then the object seems to have its original size, but when the lens is in between these two positions the object appears bigger.

a) Where is the lens when the object appears the greatest?

b) What is the focal length of the lens, if when the object appears the greatest, its observed size is twice as big as its original size?

(5 pont)

Deadline expired on March 10, 2014.

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

Megoldásvázlat. $\displaystyle a)$ A legnagyobb látószögben akkor látjuk a tárgyat, amikor a lencse a szemünktől 15 cm-re van.

$\displaystyle b)$ $\displaystyle f=15$ cm.

### Statistics:

 9 students sent a solution. 5 points: Balogh Menyhért, Fehér Zsombor, Janzer Barnabás, Trócsányi Péter. 4 points: Antalicz Balázs, Bugár 123 Dávid. 3 points: 1 student. 1 point: 2 students.

Problems in Physics of KöMaL, February 2014