An optical fiber consists of a cylindrical dielectric rod of refractive index $$n_1$$, surrounded by another dielectric of refractive index $$n_2$$ where $$n_2$$ < $$n_1$$ as shown in the following Fig. If a ray is incident from air at angle i to the axis, then it undergoes total internal reflection at the interface AB if

Choose the correct statements.
For a wave propagating in an air filled rectangular wave guide

For a normal mode EM wave propagating in a hollow rectangular wave guide

The cut-off frequency of a waveguide depends upon