Question

why are potassium and calcium rather than lithium used in photoelectric cell​

Answer 1

Answer:

Hey,

Photoelectric cells are made up of elements which readily gives out electrons when Sunlight falls on them.

But lithium has a small size ,and the electrons are attracted by great Nuclear charge.Due to which Electrons cannot escape .They require more energy. Hence Lithium is not used.

Answer 2

Answer:

The ionization potentials of potassium and cesium are lower than that of lithium. On exposure to light, potassium and caesium easily emit electrons however lithium does not. Hence, potassium and caesium are used in the photoelectric cell.