$A$ light emitting diode $(LED)$ has a voltage drop of $2\,V$ across it and passes a current of $10\,mA$ when it operates with a $6\,V$ battery through a limiting resistor $R$. The value of $R$ is $......\,k\Omega$.

Given below are two statements: one is labeled as Assertion $A$ and the other is labeled as Reason $R$.
Assertion $A:$ Photodiodes are used in forward bias usually for measuring the light intensity.
Reason $R:$ For a $p-n$ junction diode, at applied voltage $V$, the current in the forward bias is more than the current in the reverse bias for $|V_z| > |V| \geq V_0$, where $V_0$ is the threshold voltage and $V_z$ is the breakdown voltage.
In the light of the above statements, choose the correct answer from the options given below.

$A$ photodiode is a device

For the emission of light,a light emitting diode $(LED)$ is:

On which principle does the $Vidicon$ work?

The $I-V$ characteristic of an $LED$ is represented by which of the following graphs?