An equiconvex lens of refractive index  $n_2$ is placed such that the refractive index of the surrounding media is as shown. Then the lens:

must be converging if  $n_2$ is greater than the arithmetic mean of  $n_{1}and{n}_3$

must be diverging if  $n_2$ is less than the arithmetic mean of  $n_{1}and{n}_3$

must be diverging if $n_2$  is less than the arithmetic mean of  $n_{1}and{n}_3$

Will neither be diverging nor converging if  $n_2$  is equal to arithmetic mean of  $n_{1}and{n}_3$