The emf of the following three galvanic cells are represented by ${\mathrm{E}}_1,{\mathrm{E}}_2\text{ and }{\mathrm{E}}_3$ respectively. Which of the following is correct? 
i) $\mathrm{Zn}/{\mathrm{Zn}}^{2+}\left(1\mathrm{M}\right)//{\mathrm{Cu}}^{2+}\left(1\mathrm{M}\right)/\mathrm{Cu}$

ii) $\mathrm{Zn}/{\mathrm{Zn}}^{2+}\left(0.1\mathrm{M}\right)//{\mathrm{Cu}}^{2+}\left(1\mathrm{M}\right)/\mathrm{Cu}$

iii) $\mathrm{Zn}/{\mathrm{Zn}}^{2+}\left(1\mathrm{M}\right)//{\mathrm{Cu}}^{2+}\left(0.1\mathrm{M}\right)/\mathrm{Cu}$

The E_cell of a galvanic cell is related to the concentration is given by Nernst equation. 

${\mathrm{E}}_{\mathrm{cell}}={\mathrm{E}}^{\mathrm{o}}-\frac{0.0591}{\mathrm{n}}{\log }_{10}\frac{\left[\mathrm{anode}\right]}{\mathrm{cathode}}$

For the given galvanic cell the Nernst equation is given as 

${\mathrm{E}}_{\mathrm{cell}}={\mathrm{E}}^{\mathrm{o}}-\frac{0.0591}{2}{\log }_{10}\frac{\left[{\mathrm{Zn}}^{2+}\right]}{\left[{\mathrm{Cu}}^{2+}\right]}$

With an increase in the concentration of Zn²⁺ ions, the emf of cell decreases.
With increase in the concentration of Cu²⁺ ions, the emf of cell increases.

Therefore, E₂> E₁>E₃.