To calculate the energy of a photon of violet light, we use the following parameters:

Wavelength of violet light, $\lambda = 4000 \ \text{\AA} = 4000 \times 10^{-10} \ \text{m}$

Planck's constant, $h = 6.63 \times 10^{-34} \ \text{J} \cdot \text{s}$

Speed of light, $c = 3 \times 10^8 \ \text{m/s}$

The energy $E$ of a photon is given by the formula:

$$E = \frac{hc}{\lambda}$$

Substituting the values into the equation:

$$ \begin{aligned} E &= \frac{6.63 \times 10^{-34} \times 3 \times 10^8}{4000 \times 10^{-10}} \\ &= \frac{19.89 \times 10^{-26}}{4 \times 10^{-7}} \\ &= 4.9725 \times 10^{-19} \ \text{J} \end{aligned} $$

To convert this energy into electron-volts (eV), we divide by $1.6 \times 10^{-19} \ \text{J/eV}$:

$$ \begin{aligned} E &= \frac{4.9725 \times 10^{-19}}{1.6 \times 10^{-19}} \ \text{eV} \\ &\approx 3.11 \ \text{eV} \end{aligned} $$

Therefore, the energy of the violet light photon is $4.97 \times 10^{-19} \ \text{J}$ or approximately $3.11 \ \text{eV}$.