"prime" symbol too low if within square root

Question

I have a formula using "E-prime-squared", i.e., E'². Unfortunately, the prime descendes if this is written within a formula:

\documentclass{article}

\begin{document}

This looks nice: $E'$,
and while this is okay: $E'^2$,
this is probably better: ${E'}^2$,
but this is ugly: $\sqrt{E'^2}$,
and this as well: $\sqrt{{E'}^2}$.

\end{document}

This results in: Is there any way to prevent LaTeX from lowering the prime symbol?

Answer 1

This is the so called cramped style, in luatex you can escape it but in classic tex you need to re-start a nested math list to avoid it.

\documentclass{article}

\begin{document}

This looks nice: $E'$,
and while this is okay: $E'^2$,
this is probably better: ${E'}^2$,
but this is ugly: $\sqrt{E'^2}$,
and this as well: $\sqrt{{E'}^2}$.
But $\sqrt{\hbox{$E'^2$}}$.

\end{document}

Or you could adjust the font parameters so cramped setting is not so cramped....