In photoelectric effect, if the energy required to overcome the attractive forces on the electron, (work functions) of Li, Na and Rb are 2.41 eV, 2.30 eV and 2.09 eV respectively, the work function of ‘K’ could approximately be in eV.

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2.52

2.01

2.35

2.20

answer is B.

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Detailed Solution

Larger atoms have easy tendency to loose electrons.

As the size of the atom increases, the energy required to overcome the attractive force on outermost electron decreases.

Li,Na,K and Rb are the members of the same group and have the following order of size:
Hence Li<Na<K<Rb

Thus, the energy in case of K is intermediate of Rb and Na, i.e.,

2.30 > K > 2.09 or the energy for K is 2.20 eV.

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