Question #43461

A logic circuit consists of a two-input NAND gate with infinite input impedance. The gate registers a logic HIGH (1) if the input voltage $V \ge 2.0 \text{ V}$ relative to ground, and a logic LOW (0) if $V < 2.0 \text{ V}$. Input A is connected to the cathode of photoelectric Cell A, and Input B is connected to the cathode of photoelectric Cell B. The anodes of both cells are grounded. Cell A has a work function $\Phi_A = 2.5 \text{ eV}$ and is illuminated by light of variable frequency $\nu_A$. Cell B has a work function $\Phi_B = 2.2 \text{ eV}$ and is illuminated by light of fixed wavelength $\lambda_B = 310 \text{ nm}$ with a continuously increasing intensity $I_B$. Initially, $\nu_A$ is zero. What is the minimum frequency $\nu_A$ required to switch the NAND gate output from HIGH (1) to LOW (0)? (Take $hc = 1240 \text{ eV}\cdot\text{nm}$ and Planck's constant $h = 4.14 \times 10^{-15} \text{ eV}\cdot\text{s}$)