According to the question,
By using Gauss law,
→ [tex]E(r)\ \phi \ dA = \frac{q}{\varepsilon_0}[/tex]
or,
→ [tex]E(r) (2 \pi r L) = \frac{q}{\varepsilon_0}[/tex]
[tex]E(r) = \frac{1}{2 \pi r \varepsilon_0} (\frac{q}{L} )[/tex]
[tex]E(r) = \frac{\lambda}{2 \pi \varepsilon_0 r}[/tex]
Thus the approach above is appropriate.
Learn more about cylindrical rod here:
https://brainly.com/question/10727798