Assertion (A): We cannot form a p-n junction ...

CBSE Class 12 Physics 2025 All Sets Solved Paper

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Assertion (A): We cannot form a p-n junction diode by taking a slab of a p-type semiconductor and physically joining it to another slab of a n-type semiconductor.

Reason (R): In a p-type semiconductor

\eta_e \gg \eta_h

while in a n-type semiconductor

\eta_e \gg \eta_h

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A)
Assertion (A) is true, but Reason (R) is false
Assertion (A) is false and Reason (R) is also false

Solution:

Assertion (A): True : A p-n junction cannot be formed just by joining p-type and n-type semiconductors physically due to lack of diffusion and formation of a depletion region.

Reason (R): False : In a p-type semiconductor

\eta_e \ll \eta_h

while in a n-type semiconductor

\eta_h \ll \eta_e

also electron and hole concentrations do not justify why a p-n junction cannot form this way.

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