If the energy gap of a semiconductor used for the fabrication of an LED is nearly 1.9 eV , then the color of the light emitted by the LED is

$10^{10}$ electrons enter the emitter of a junction transistor in a time of $0.4 \mu \mathrm{~s}$. If $5 \%$ of the electrons are lost in the base, then the collector current is

An electron in $n$-region of a $p-n$ junction moves towards the junction with a speed of $5 \times 10^5 \mathrm{~ms}^{-1}$. If the barrier potential of the junction is 0.45 V , then the speed with which the electron enters the $p$-region after penetration through the barrier is

(Charge of the electron $=1.6 \times 10^{-19} \mathrm{C}$ and mass of the electron $=9 \times 10^{-31} \mathrm{~kg}$ )

The power gain and voltage gain of a transistor connected in common emitter configuration are 1800 and 60 respectively. If the change in the emitter current is 0.62 mA , then the change in the collector current is