When wavefronts pass from a denser medium to a rarer medium, the width of the wavefront

Huygens' wave theory allows us to know

The figure shows a surface $XY$ separating two transparent media,medium-$1$ and medium-$2$. The lines $ab$ and $cd$ represent wavefronts of a light wave travelling in medium-$1$ and incident on $XY$. The lines $ef$ and $gh$ represent wavefronts of the light wave in medium-$2$ after refraction.
$1.$ Light travels as a
$(A)$ parallel beam in each medium
$(B)$ convergent beam in each medium
$(C)$ divergent beam in each medium
$(D)$ divergent beam in one medium and convergent beam in the other medium.
$2.$ The phases of the light wave at $c, d, e$ and $f$ are $\phi_{c}, \phi_{d}, \phi_{e}$ and $\phi_{f}$ respectively. It is given that $\phi_{c} \neq \phi_{f}$.
$(A)$ $\phi_{c}$ cannot be equal to $\phi_{d}$
$(B)$ $\phi_{a}$ can be equal to $\phi_{e}$
$(C)$ $(\phi_{d}-\phi_{c})$ is equal to $(\phi_{f}-\phi_{e})$
$(D)$ $(\phi_{d}-\phi_{c})$ is not equal to $(\phi_{f}-\phi_{e})$
$3.$ Speed of the light is
$(A)$ the same in medium-$1$ and medium-$2$
$(B)$ larger in medium-$1$ than in medium-$2$
$(C)$ larger in medium-$2$ than in medium-$1$
$(D)$ different at $b$ and $d$
Give the answer for questions $1, 2$ and $3$.

Which of the following phenomena cannot be explained by Huygens' principle?

Huygens' theory of secondary waves can be used to find:

The wavefront of a wave has what direction with respect to the wave motion?