Correct Answer - Option 2 : 1 nA
The very small current flows through the diode when the diode is in the reverse-biased state is called the reverse current of the diode.
The reverse saturation current of a silicon diode is of the order of nano amperes (nA). ∴ The silicon diode is operated as a good switch.
The reverse saturation current of a Germanium diode is of the orders of micro-amperes (μA).
Reverse Bias: When the case is opposite and n-type side is kept at a higher potential than the p-type side, only a small amount of reverse saturation current flows through the diode, referring to this condition as reverse biased.
Forward Bias: When the p-type side of the diode is connected to a higher potential than the n-type side, the diode is said to be forward-biased, because it enhances the capability of the diode to conduct forward current.