The figure shows $2$ $LEDs$ that can be used as a polarity detector. Applying a positive source voltage results in a green light,while negative supplies result in a red light. Packages of such combinations are commercially available. Find the resistor $R$ to ensure a current of $20 \ mA$ through the $ON$ diode for the configuration. Both diodes have a reverse breakdown voltage of $3 \ V$ and an average turn-on voltage of $2 \ V$. The source voltage is $8 \ V$. Find $R$ in $\Omega$.

$A$ 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 $......\,k\Omega$.

With increasing biasing voltage of a photodiode,the photocurrent magnitude

The $I-V$ characteristic of an $\text{LED}$ is $:$

$A$ $p-n$ photodiode is made of a material with a band gap of $2.0\, eV$. The minimum frequency of the radiation that can be absorbed by the material is nearly:

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.