When light in material $1,$ which is in contact with material $2,$ undergoes total internal reflection, what condition is necessary for their indices of refraction?

Multiple Choice

$$

$n_1=2n_2$

$n_1>n_2$

$n_1=n_2+1n_2=1\mathrm{.}5n_1$

$$

$n_1=n_2+1$

$$

$n_2=1\mathrm{.}5$