LED is constructed from $Ga-As-P$ semiconducting material. The energy gap of this LED is $1.9 \mathrm{eV}$. Calculate the wavelength of light emitted and its colour. $h=6.63\times {10}^{-34} \mathrm{J}-\mathrm{s}$ and $c=3\times {10}^8 \mathrm{m} {\mathrm{s}}^{-1}$

A zener diode of power rating $2 \mathrm{W}$ is to be used as a voltage regulator. If the zener diode has a breakdown of $10 \mathrm{V}$ and it has to regulate voltage fluctuated between $6 \mathrm{V}$ and $14 \mathrm{V}$, the value of $R_s$ for safe operation should be _____ $\Omega$ .

A circuit is arranged as shown in figure. The output voltage $V_o$ is equal to __________ $\mathrm{V}.$

For the given circuit, the power across zener diode is _____ $\mathrm{mW}$.