The natural frequency of a mass m at the end of the cantilever beam of negligible mass with usual notations will be
1
\(\frac{1}{{2\pi }} \;{\left( {\frac{{3EI}}{{m{l^3}}}} \right)^{\frac{1}{2}}}\)
2
\(\frac{1}{\pi }{\left( {\frac{{6EI}}{{m{l^3}}}} \right)^{\frac{1}{2}}}\)
3
\(\frac{1}{{2\pi }}\;{\left( {\frac{{6EI}}{{m{l^3}}}} \right)^{\frac{1}{2}}}\)
4
\(\frac{1}{\pi }{\left( {\frac{{3EI}}{{m{l^3}}}} \right)^{\frac{1}{2}}}\)