Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : The photoelectric effect does not take place, if the energy of the incident radiation is less than the work function of a metal.
Reason R : Kinetic energy of the photoelectrons is zero, if the energy of the incident radiation is equal to the work function of a metal.
In the light of the above statements, choose the most appropriate answer from the options given below.

• A. Both A and R are correct and R is the correct explanation of A
• B. Both A and R are correct but R is not the correct explanation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Answer 1

Answer: (B)

To free the electron from metal surface minimum energy required, is equal to the work function of that metal.
So Assertion $A$, is correct.
$h v = w _{0}+ K . E _{\max }$
if $hv = w _{0}$
$\Rightarrow \text { K.E. }_{\max }=0$
Hence reason $R$, is correct, But $R$ is not the correct explanation of $A$.