# Why is light wavelength measured in nm?

Of course you can convert it into metres if you wished, but photon energy is measured as such:

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

In this scenario, Energy is measured in electron volts. But if we measured light in metres, wouldn't we get joules since we are using SI units? However, when converting between $$eV$$ and $$J$$ it's not a matter of place value, i.e one isn't $$\times10^n$$. What's causing this?

\begin{align} 1\,\mathrm{eV}&=1.602176634\times 10^{-19}\,\mathrm{C}\cdot\mathrm{V}=\\ &=1.602176634\times 10^{-19}\,\mathrm{J}. \end{align}