An $LED$ is a $p-n$ junction diode which is

Three photodiodes $D_{1}, D_{2}$ and $D_{3}$ are made of semiconductors having band gaps of $2.5 eV, 2 eV$ and $3 eV$,respectively. Which one will be able to detect light of wavelength $600 nm$?

$A$ $p-n$ 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:

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

Statement $-I$: $A$ photodiode operates in reverse bias.
Statement $-II$: The fractional change due to the photo-effects on the minority carrier dominated reverse bias current is more easily measurable than the fractional change in the forward bias current.

$A$ light emitting diode $(LED)$ is fabricated using $GaAs$ semiconducting material whose band gap is $1.42 \,eV$. The wavelength of light emitted from the $LED$ is: (in $\,nm$)