[填空题]
1.Light falls on a photakht.v*h 0d( vy*6 nsqoelectric surface with a i qi-o+ k/q *ymm 1qlkua+fd5:threshold frequency of $5.2\times10^{14}\,Hz$.
State what is meant by photoelectric emission.
2.(1)Calculate the work function of the photoelectric surface in electronvolts. $ϕ$ = $eV$
(2)The ammeter gives a reading when a violet light is used, while it reads zero when a red light with the same intensity is used. Explain this observation.
(3)The frequency of violet photons is $7.5\times10^{14}\,Hz$. Calculate the maximum speed of the emitted electrons.
3.On the axes below, sketch the variation of the photoelectric current with the potential difference for an incident frequency above the threshold frequency. Also label the stopping voltage $V_s$. v = $\times10^5\,ms^{-1}$
