Question

Given below are two statements : one is labelled as AssertionA and the other is labelled as ReasonR.

Assertion A : The photoelectric effect does not takes 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

The Correct Option is B

To determine the correct answer, let's evaluate both the Assertion (A) and the Reason (R) statements one by one. 

• 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.
  • This assertion is correct. The photoelectric effect occurs when photons hit a metal surface and cause the emission of electrons. The energy of the incident radiation must be equal to or greater than the work function of the metal for the electrons to be emitted. The work function is the minimum energy required to release an electron from the surface. If the energy of the photon is less than the work function, the electrons will not have sufficient energy to escape, and thus, the photoelectric effect will not occur.
• 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.
  • This reason is also correct. When the energy of the incident radiation (photon energy) is precisely equal to the work function of the metal, the electron just barely escapes the metal surface with zero kinetic energy. The entire photon energy is used to overcome the work function, leaving no extra energy as kinetic energy for the photoelectrons.

While both the Assertion and the Reason are true, the statement in the Reason does not directly explain the Assertion. The assertion discusses the case when the energy of the incident radiation is less than the work function, leading to no photoelectric effect. In contrast, the reason talks about the condition when the energy is equal to the work function, resulting in zero kinetic energy but not necessarily contributing towards explaining why no photoelectric effect occurs when the energy is insufficient.

Therefore, the correct answer is that Both A and R are correct but R is not the correct explanation of A.