The minimum value of the refractive index for a ${90}^{\circ }-{45}^{\circ }-{45}^{\circ }$ prism that is used to deviate a beam by ${90}^{\circ }$ by the phenomenon of total internal reflection is ________.

Q. The minimum value of the refractive index for a ${90}^{\circ }-{45}^{\circ }-{45}^{\circ }$ prism that is used to deviate a beam by ${90}^{\circ }$ by the phenomenon of total internal reflection is ________.

Q. The minimum value of the refractive index for a 90° – 45° – 45° prism which is used to deviate a beam by 90° by the phenomenon of total internal reflection is ____

Q. What is the minimum value of the refractive index for a ${90}^{\circ }–{45}^{\circ }–{45}^{\circ }$ prism
which is used to deviate a beam through ${90}^{\circ }$ by total internal reflection ?

Q. The minimum value of refractive index of the material of the prism for which the ray (1) under goes total internal reflection on the face AC is:

Q. A parallel beam of light is incident from air at an angle a on the side $PQ$ of a right-angled triangular prism of refractive index $n=\sqrt{2}$. The beam of light undergoes total internal reflection in the prism at the face $PR$ when a has a minimum value of ${45}^{\circ }$. The angle $\theta$ of the prism is