Which semiconductor device converts electrical energy into light?

Which one of the following symbols represents a photodiode?

Which wavelength of the Sun is primarily used to generate electric energy in solar cells?

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

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 ones will be able to detect light of wavelength $6000 \ \mathring{A}$?

The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than $2480 \; nm$ is incident on it. The band gap in $eV$ for the semiconductor is