The semiconductor used for fabrication of visible LEDS must at least have a band gap of

In a common emitter amplifier, AC current gains 40 and input resistance is $2 \mathrm{k} \Omega$. The load resistance is given as $10 \mathrm{k} \Omega$. Then, the voltage gain is

An information signal of frequency 10 kHz is modulated with a carried wave of frequency $3.62 \mathrm{MHz}^{}$ The upper side and lower side frequencies are

The time period of revolution of a satellite $T$ around the carth depends on the radius of the circular orbit $R$. mass of the earth $M$ and universal gravitational constant $G$. The expression for $T$, using dimensional analysis is ( $K$ is constant of proportionality)