Mathematical and Physical Journal
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# Problem P. 4757. (September 2015)

P. 4757. The work function of the cathode of a photocell in a circuit is $\displaystyle 6\cdot 10^{-19}$ J. Ultraviolet wave of wavelength 250 nm hits the cathode perpendicularly.

$\displaystyle a)$ What is the stopping potential at which the photo-current becomes zero?

$\displaystyle b)$ What is the linear momentum given to the cathode, during one elementary process, if the emitted electron is ejected oppositely to the direction of the radiation?

$\displaystyle c)$ Let us change the frequency of the radiation. At most by what factor can the linear momentum of the emitted electron be greater than that of the entering photon?

(5 pont)

Deadline expired on October 12, 2015.

### Statistics:

 59 students sent a solution. 5 points: Balogh Menyhért, Blum Balázs, Forrai Botond, Kovács Péter Tamás, Németh Flóra Boróka, Tomcsányi Gergely. 4 points: Asztalos Bogdán, Baglyas Márton, Bartók Imre, Boldizsár Bálint, Büki Máté, Csire Roland, Csorba Benjámin, Di Giovanni András, Elek Péter, Fekete Balázs Attila, Gémes Antal, Gergely 444 Kornél, Iván Balázs, Jakus Balázs István, Kádár 012 István, Kasza Bence, Klász Viktória, Kolontári Péter, Körmöczi Dávid, Körtefái Dóra, Krasznai Anna, Nagy 555 Botond, Olosz Adél, Páhoki Tamás, Pázmán Előd, Riskutia Balázs, Sal Kristóf, Sallai Krisztina, Szántó Benedek, Szentivánszki Soma , Tófalusi Ádám, Tompa Tamás Lajos, Tóth Adrián, Varga-Umbrich Eszter, Zalavári Márton. 3 points: 10 students. 2 points: 3 students. 1 point: 5 students.

Problems in Physics of KöMaL, September 2015