During positive half cycle of input ac voltage, the p-n junction is forward biased, the resistance of p-n junction is low. The current in the circuit is maximum. In this situation, a maximum potential difference will appear across resistance connected in series of circuit. Due to it, there is no output voltage across p-n junction.

During the negative half- cycle of input ac voltage, the p-n junction is reverse biased. The resistance of p-n junction becomes high which will be more than resistance in series. Due to it, there will be voltage across p-n junction with negative cycle in output.