X-rays of wavelength, $\lambda=1 Å$ have frequency:

$3 \times 10^{14}$ Hz $1 \times 10^{15}$ Hz $3 \times 10^{16}$ Hz $3 \times 10^{18}$ Hz

$3 \times 10^{18}$ Hz

The correct answer is Option (4) → $3 \times 10^{18}$ Hz