Assertion (A): Light emitting diode (LED) emits self radiation.
Reason (R): LED are reverse biased p-n junctions.
Concept: LED operation.
LEDs are \(p-n\) junctions that emit light when forward biased due to electron-hole recombination. Reverse biasing does not cause light emission. Thus, Assertion (A) is true, but Reason (R) is false.
Assertion (A): Conductivity of intrinsic semiconductor is less as compared to extrinsic semiconductor.
Reason (R): With increase in temperature conductivity of semiconductor increases.
Concept: Semiconductor conductivity.
Intrinsic semiconductors have fewer free charge carriers than extrinsic (doped) semiconductors, so (A) is true. Increasing temperature generates more carriers in semiconductors, increasing conductivity, so (R) is true. However, (R) describes temperature dependence, not the difference between intrinsic and extrinsic. Thus, (R) is not the correct explanation for (A).
Assertion (A): Avalanche breakdown dominates when the doping concentration is high and depletion layer is thin.
Reason (R): Zener breakdown occurs due to the collision of minority charge carrier.
Concept: \(p-n\) junction breakdown.
Avalanche breakdown occurs in lightly doped junctions with wider depletion regions. Zener breakdown occurs in heavily doped junctions due to quantum tunneling, not minority carrier collisions. Thus, both (A) and (R) are false.
Assertion (A): Semiconductors do not obey Ohm’s law.
Reason (R): Electric current is determined by the rate of flow of charge carriers.
Concept: Ohm's Law and current definition.
Semiconductors are non-ohmic devices, so (A) is true. Electric current is indeed the rate of flow of charge, \(I = \frac{dQ}{dt}\), so (R) is true. However, (R) is a definition of current and does not explain why semiconductors are non-ohmic. Thus, (R) is not the correct explanation of (A).
Assertion (A): The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature decreases exponentially with increasing band gap.
Reason (R): It is more difficult for the electrons to jump to the conduction band from the valence band if the band gap between them is large.
Assertion (A) is true: The probability of finding electrons in the conduction band is proportional to \(e^{-E_g / (2kT)}\), decreasing exponentially with band gap \(E_g\).
Reason (R) is true: A larger band gap means more energy is required for electrons to jump. Reason (R) correctly explains Assertion (A).
Assertion (A): The logic gate NOT can not be built using diode.
Reason (R): The output voltage and the input voltage of the diode does not have \(180^{\circ}\) phase difference.
Assertion (A) is true because a NOT gate requires active components to provide inversion and gain, which a passive diode cannot do. Reason (R) is true because a diode circuit does not inherently provide the \(180^{\circ}\) phase shift characteristic of logic inversion. Thus, (R) correctly explains (A).