K.C.S.E Physics Q & A - MODEL 2015PP2QN14

K.C.S.E Physics Q & A - MODEL 2015PP2QN14

(a) State two factors that affect photoelectric emission.
(b) Light of wavelength 4.3 x 10^-7m is incident on two different metal surfaces, nickel and potassium. (Take speed of light as 3.0 x 10⁸ ms^-1 and planks constant h as 6.63 x 10^-34Js).

(i) Determine the energy of the incident radiation.
(ii) If the work function of nickel is 8.0 x 10^-19J and that of potassium is 3.68 x 10^-19J, state with a reason from which of the two metals the given light will eject electrons.
(iii) Determine the velocity of the emitted electrons from the metal surface in b(ii).
(Take the mass of an electron as 9.1 x 10^-31 kg).

answers

(a) Energy of incident radiation
Work function of the metal
Intensity of the radiation

​(ii) Potassium
The work function of potassium is less than the energy of the incident radiation