JEE Main 2023 — Structure Of Atom Question with Solution

Given are two statements :

• Assertion A : "In the photoelectric effect, the electrons are ejected from the metal surface as soon as the beam of light of frequency greater than threshold frequency strikes the surface."
• Reason R : "When the photon of any energy strikes an electron in the atom, transfer of energy from the photon to the electron takes place."

From the understanding of the photoelectric effect, we know that the light beam must have a frequency $v$ that is greater than the threshold frequency $v_0$ for electrons to be ejected from the metal surface. Therefore, Assertion A is correct.

However, Reason R is somewhat misleading in the context of the photoelectric effect. It's true that a photon transfers its energy to an electron when it strikes the electron. However, for the electron to be ejected (i.e., the photoelectric effect to occur), the energy of the photon, given by $E_{photon}=h\cdot v$, where $h$ is Planck's constant and $v$ is the frequency of the light, must be greater than the work function $\varphi$ (the minimum energy needed to eject an electron) of the metal. This condition is not captured in Reason R.

Therefore, the correct answer is :

Option C : Assertion A is correct, but Reason R is not correct.