1. Use the electromagnetic spectrum relation

   For any electromagnetic wave,

   $$$$

u = \frac{c}{\lambda}

\lambda \approx 6 \times 10^{-12}\ \text{m}

\nu = \frac{3 \times 10^8}{6 \times 10^{-12}}

\nu = \frac{3}{6} \times 10^{8-(-12)}

\nu = 0.5 \times 10^{20} = 5 \times 10^{19}\ \text{Hz}

x \times 10^{19}\ \text{Hz}

x = 5

x = 5