In a half wave rectifier, the frequency of the output is :

The correct answer is Option (2) → same as that of input

A half wave rectifier lets the current through during only one half of each input cycle (when the diode is forward biased) and blocks the other half.

So the output has one pulse for every cycle of the input. The pulses repeat with the same period \( T \) as the input, and the output frequency equals the input frequency.

Why the other options are incorrect

• Option (1) half the frequency of input — Incorrect. No input cycle is skipped, so the pulses do not repeat at half the rate.

• Option (3) twice the frequency of input — Incorrect. Twice the input frequency is the output of a full wave rectifier, which uses both halves of each cycle.

• Option (4) Zero — Incorrect. The output is a pulsating dc, not a steady one; its pulses still repeat at the input frequency.

NCERT (2026-27):
Application of Junction Diode as a Rectifier – “… So if an alternating voltage is applied across a diode the current flows only in that part of the cycle when the diode is forward biased. This property is used to rectify alternating voltages and the circuit used for this purpose is called a rectifier. If an alternating voltage is applied across a diode in series with a load, a pulsating voltage will appear across the load only during the half cycles of the ac input during which the diode is forward biased.”