Correct Option: (d) Assertion (A) is false but Reason (R) is false.

Step 1 (Conceptual Analysis of Assertion): [0.5 Mark]

The Assertion states that a p-n junction cannot be formed by physically joining two slabs. This is false. While it is technically difficult to achieve a perfect atomic-level contact due to surface roughness and lattice mismatch, the physical joining of p-type and n-type semiconductors is a valid theoretical and experimental method to create a p-n junction, provided the surfaces are polished and brought into intimate contact.

Step 2 (Conceptual Analysis of Reason): [0.5 Mark]

The Reason states that in a p-type semiconductor $n_e \gg n_h$ and in an n-type semiconductor $n_h \gg n_e$. This is false. According to NCERT standards:

• In a p-type semiconductor, holes are majority carriers and electrons are minority carriers: $n_h \gg n_e$.
• In an n-type semiconductor, electrons are majority carriers and holes are minority carriers: $n_e \gg n_h$.

The statement in the Reason has inverted the carrier concentrations.

Step 3 (Final Concluded Answer): [0.0 Mark - Integrated]

Since both the Assertion (A) and the Reason (R) are factually incorrect statements, the correct choice is (d).

💡 EL10 Concept Insight:

Think of it like this: "p-type" means "positive" (more holes), and "n-type" means "negative" (more electrons). The reason got it backwards, and you actually can make a junction by pressing two pieces together—it's just like trying to stick two pieces of tape together perfectly without any air bubbles!