In a common emitter transistor amplifier circuit, the input resistance is $1.8 \mathrm{k} \Omega$ and output is obtained across a load resistance of $9 \mathrm{k} \Omega$. The alternating current gain is 70 . Corresponding to an a.c. input voltage of 6 mV , the output voltage will be

Applying forward bias to p-n junction, the potential barrier

The material used for solar cell should have band gap

One of the following values of inputs $\mathrm{A}, \mathrm{B}$ and C respectively gives output $(\mathrm{Y})$ of the following combination of logic gates as ' 1 ' is