In which of the following circuits is the junction reverse biased?

The energy of a photon of sodium light $(\lambda = 589 \text{ nm})$ is equal to the band gap of a semiconductor. Find the minimum energy $E$ in $eV$ required to create an electron-hole pair.

The voltage gain of the following amplifier is

The amplifiers $X, Y$ and $Z$ are connected in series. If the voltage gains of $X, Y$ and $Z$ are $10, 20$ and $30$ respectively,and the input signal is $1 \, mV$ peak value,then what is the output signal voltage (peak value) $(i)$ if $DC$ supply voltage is $10 \, V$? $(ii)$ if $DC$ supply voltage is $5 \, V$?

Three amplifiers with voltage gains $10, 20$ and $30$ are connected in series. If the input signal has a peak value of $1 mV$, then the peak value of the output voltage is (in $\,V$)

Consider the following statements:
Statement $(A)$: The resistance of an ideal diode in forward biased condition is zero.
Statement $(B)$: In a half-wave rectifier,the load current flows only for every half cycle of the input signals.
Statement $(C)$: In the breakdown region,a Zener diode behaves as a constant voltage source.