\(\frac{ h }{2}=\frac{1}{2} gt _{1}^{2}\)
For total height \(h\)
\(h =\frac{1}{2} g \left( t _{1}+ t _{2}\right)^{2}\)
\(\frac{1}{\sqrt{2}}=\frac{ t _{1}}{ t _{1}+ t _{2}}\)
\(1+\frac{ t _{2}}{ t _{1}}=\sqrt{2}\)
\(\frac{ t _{1}}{ t _{2}}=\frac{1}{\sqrt{2}-1}\)
\(t _{2}=(\sqrt{2}-1) t _{1}\)