Correct Option: (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).

Step 1 (Foundational Principles): [1/3 Mark]

• Assertion (A): According to the photoelectric effect, the photoelectric current ($I$) is directly proportional to the number of photoelectrons emitted per second, which is directly proportional to the intensity ($I_{rad}$) of the incident radiation, provided the frequency ($\nu$) is above the threshold frequency ($\nu_0$).
• Reason (R): According to Einstein’s photoelectric equation: $$K_{max} = h\nu - \Phi_0 = eV_s$$ where $K_{max}$ is the maximum kinetic energy, $h$ is Planck's constant, $\nu$ is the frequency of incident light, $\Phi_0$ is the work function, and $V_s$ is the stopping potential.

Step 2 (Step-by-Step Logical Analysis): [1/3 Mark]

• Analysis of (A): Since each incident photon ejects one photoelectron, increasing the intensity (number of photons per unit area per unit time) increases the number of emitted electrons, thereby increasing the photoelectric current. Thus, (A) is true.
• Analysis of (R): From the equation $V_s = \frac{h\nu - \Phi_0}{e}$, it is evident that $V_s$ depends only on the frequency of incident radiation ($\nu$) and the material properties ($\Phi_0$). It does not contain any term related to intensity. Thus, (R) is true.

Step 3 (Final Concluded Answer): [1/3 Mark]

Both statements are scientifically correct based on the experimental observations of the photoelectric effect. However, the fact that stopping potential is independent of intensity (R) does not explain why the current depends on intensity (A). Therefore, (R) is not the correct explanation for (A).

💡 EL10 Concept Insight: Think of light like a rain shower: increasing the intensity is like making the rain heavier (more drops hitting the ground, so more current), while the stopping potential is like the speed of the raindrops—it only changes if you change the "color" (frequency) of the light, not how many drops are falling.