The frequency of a photon whose energy is 66.3 eV would be

(Given $h= 6.63 × 10^{-34} Js$)

$1.6 × 10^{16} Hz$

The correct answer is Option (3) → $1.6 × 10^{16} Hz$

$E = 66.3 \text{ eV} = 66.3 \times 1.6 \times 10^{-19} \text{ J}$

$E = 1.0608 \times 10^{-17} \text{ J}$

$E = h\nu$

$\nu = \frac{E}{h} = \frac{1.0608 \times 10^{-17}}{6.63 \times 10^{-34}}$

$\nu = 1.6 \times 10^{16} \text{ Hz}$

Final Answer: $1.6 \times 10^{16} \text{ Hz}$