When a forward bias is applied to a $p-n$ junction,what happens to the potential barrier?

How does the height of the potential barrier change in forward bias and reverse bias?

$PN-$junction diode works as an insulator if connected:

The depletion layer in a silicon diode is $1 \, \mu m$ wide and the knee potential is $0.6 \, V$. The electric field in the depletion layer is:

The junction diode in the following circuit requires a minimum current of $1 \, mA$ to be above the knee point $(0.7 \, V)$ of its $I-V$ characteristic curve. The voltage across the diode is independent of current above the knee point. If $V_B = 5 \, V$,then the maximum value of $R$ so that the voltage is above the knee point will be:

The value of net resistance of the network as shown in the given figure is: