The energy gap of silicon is $1.1 \, eV$. At what wavelength will silicon stop absorbing photons? (in $\mathring A$)

For a crystal system where $a = b = c$ and $\alpha = \beta = \gamma \neq 90^\circ$,the system is:

Choose the correct statement. In semiconductors,the valence band and conduction band

GaAs is

If $V_0$ is the volume of a standard unit cell of germanium crystal containing $N_0$ atoms, then the expression for the mass $m$ of a volume $V$ in terms of $V_0, N_0, M$ and $N_A$ is [here, $M$ is the molar mass of germanium and $N_A$ is the Avogadro's constant].

$Sn, C, Si$,and $Ge$ are all group $XIV$ elements. Yet,$Sn$ is a conductor,$C$ is an insulator,while $Si$ and $Ge$ are semiconductors. Why?