For a transistor, $\alpha_{\mathrm{dc}}$ and $\beta_{\mathrm{dc}}$ are the current ratios, then the value of $\frac{\beta_{\mathrm{dc}}-\alpha_{\mathrm{dc}}}{\alpha_{\mathrm{dc}} \times \beta_{\mathrm{dc}}}$

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