On increasing the reverse bias to a large value in a $P-N$ junction diode,current

In a reverse biased diode, when the applied voltage changes by $1 \, V$, the current is found to change by $0.5 \, \mu A$. The reverse bias resistance of the diode is

In a $PN-$ junction diode not connected to any circuit:

The figure shows a circuit in which three identical diodes are used. Each diode has a forward resistance of $20\,\Omega$ and an infinite backward resistance. Resistors $R_1 = R_2 = R_3 = 50\,\Omega$. The battery voltage is $6\,V$. The current through $R_3$ is.....$mA$.

The barrier potential of a $p-n$ junction depends on:
$(1)$ Type of semiconductor material
$(2)$ Amount of doping
$(3)$ Temperature
Which one of the following is correct?

$A$ silicon diode has a forward voltage drop of $1.2\, V$ for a forward $DC$ current of $100\, mA$. It has a reverse current of $1\times10^{-6}\, A$ for a reverse voltage of $10\, V$. The bulk and reverse resistances of the diode are: