When a forward bias is applied to a $p-n$ junction,it

With forward bias mode,the $p-n$ junction diode

In forward bias,the width of the potential barrier in a $P-N$ junction diode:

In the following diode circuits,which diode is in a forward-biased condition?

The depletion layer in $p-n$ junction region is caused by

$A$ $2 \text{ V}$ battery is connected to a diode in forward bias. $A$ voltage of $0.5 \text{ V}$ is dropped across the diode,which is independent of the current flowing through it. $A$ current greater than $10 \text{ mA}$ causes excessive heating and damages the diode. If a current of $5 \text{ mA}$ is required in the diode,what value of series resistance must be connected in the circuit?