The toughness $t(G)$ of a graph $G=(V,E)$ is defined as $t(G)=\min\{\frac{|S|}{c(G-S)}\}$, in which the minimum taken over all $S\subset V$ such that $G-S$ disconnected, where $c(G-S)$ denotes number components $G-S$. We present two tight lower bounds for terms Laplacian eigenvalues and provide strong support conjecture better bound which, if true, implies both bounds, improves generalizes know...