NEET Semiconductor Physics MCQs & PYQs

A full-wave rectifier produces two positive output pulses for every single full cycle of the input AC signal. Therefore, the fundamental ripple frequency is twice the input frequency, yielding $2 \times 50 = 100$ Hz.

Statement (A) is correct as Zener diodes exclusively operate in the reverse breakdown region for voltage regulation. Statement (B) is incorrect because the typical potential barrier is around $0.7$ V for Silicon and $0.3$ V for Germanium, not restricted to $0.1$ V to $0.3$ V.

A Zener diode is heavily doped to operate safely in the reverse breakdown region. Once breakdown occurs, it maintains a near-constant voltage across its terminals despite large variations in current, making it ideal for voltage stabilisation.

When connected in reverse bias in parallel with a load, a Zener diode provides a constant DC output voltage regardless of minor fluctuations in the input DC voltage or load current, functioning perfectly as a D.C. voltage stabilizer.

The photo-electromotive force generated in a photocell is directly proportional to the number of electron-hole pairs created per second. This pair generation rate depends strictly on the number of incident photons, which defines the intensity of the incident light.

According to the Child-Langmuir law governing thermionic diodes (electronic valves) in the space-charge limited region, the plate current is directly proportional to the three-halves power of the plate voltage, establishing the relationship $I \propto V^{3/2}$.

In an unbiased p-n junction, the depletion layer is formed by the diffusion of majority carriers across the junction. This process leaves behind a region entirely depleted of mobile charge carriers, containing only immobile, static positive and negative ions.

In a half-wave rectifier, the output frequency is exactly equal to the input AC frequency because one output pulse occurs for every full cycle of the input. Thus, the output frequency remains $60$ Hz.