I’m on my phone and it’s tricky to quote. For the first part, the middle step is missing some zeros, but an easy approximate formula for wavelength is frequenc

I’m on my phone and it’s tricky to quote. For the first part, the middle step is missing some zeros, but an easy approximate formula for wavelength is frequency in Hz/3e8 m/s (rough speed of light). For the second part, that depends on whether you’re looking at voltage or power. (Because power is proportional to voltage^2, the factor of two gets pulled out)