$A$ photodiode is a device:

Which of the following statements is true about LEDs?

The following graph represents:

In optical fiber communication, an $APD$ semiconductor is used for:

$A$ $p-n$ junction is fabricated from a semiconductor with a band gap of $2.8 \ eV$. What approximate wavelength can it $NOT$ detect (in $nm$)?
[Use $h = 6 \times 10^{-34} \ J \cdot s$ and $c = 3 \times 10^8 \ m/s$]

Consider the following statements $:$
$A.$ The junction area of a solar cell is made very large compared to a photodiode.
$B.$ Solar cells are not connected with any external bias.
$C.$ $\text{LED}$ is made of heavily doped $p-n$ junction.
$D.$ Increase of forward current results in continuous increase of $\text{LED}$ light intensity up to a saturation point.
$E.$ $\text{LED}$ must be connected in forward bias for the emission of light.
Which of the following statements are correct?