Question

Which of the following elements cannot be used for photoelectric effect?

• A. $K$
• B. $Cs$
• C. $Li$
• D. Both (a) and (b)

Answer 1

Answer: (C)

$K$ and $Cs$ are used in photoelectric cells because they have very low ionisation energies but, lithium having very high ionisation energy cannot be used for photoelectric effect.