(d) $\mathrm{\Delta}\lambda = \lambda_{K_{\alpha}} - \lambda_{\min}$ When $V$ is halved $\lambda_{\min}$ becomes two time but $\lambda_{K_{\alpha}}$ remains the same.
$\therefore\mathrm{\Delta}\lambda^{'} = \lambda_{K_{\alpha}} - 2\lambda_{\min} = 2(\Delta\lambda) - \lambda_{K_{\alpha}}$
$\therefore\mathrm{\Delta}\lambda^{'} < 2(\Delta\lambda)$