In the figure, light initially in material $1$ refracts into material $2,$ crosses that material, and is then incident at the critical angle on the interface between materials $2$ and $3.$ The indices of refraction are $n_1=1\mathrm{.}56,n_2=1\mathrm{.}34,n_3=1\mathrm{.}18.($a$)$ What is angle $?($b$)$ If $$ is increased, is there refraction of light into material $3?$

$($a$)$ Number

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$($b$)$

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