Given: m = 555 g, the mass of water in the calorimeter ΔT = 39.5 - 20.5 = 19 °C, temperature change c = 4.18 J/(°C-g), specific heat of water
Assume that all generated heat goes into heating the water. Then the energy released is Q = mcΔT = (555 g)*(4.18 J/(°C-g)*(19 °C) = 44,078.1 J = 44,100 J (approximately)
They provide a source of electrons to be released by the photoelectric effect, and They provide a path through which released electrons move to form an electric current.