The figure shows a glass tube (linear co-efficient of expansion is $\alpha$) completely filled with a liquid of volume expansion co-efficient $\gamma$. On heating length of the liquid column does not change. Choose the correct relation between $\gamma$ and $\alpha$ 

 When length of the liquid column remains constant, then the level of liquid moves down with respect to the container, thus  must be less than 3. 
Now we can write V = V₀(1 + $\gamma$$∆$T)
Since V = Al₀ = [A₀ (1 + 2$\alpha ∆$T)]l₀ = V₀ (1 + 2$\alpha ∆$T)
Hence V₀(1 +$\gamma$$∆$ T) = V₀(1 + 2$\alpha ∆$T) $\Rightarrow \gamma$ = 2$\alpha$