When a plane wave front is incident on a concave mirror as shown in the figure,what is the shape of the reflected wave front?

Explain the refraction of a plane wavefront by a thin convex lens.

Explain the wavefront and its types.

Explain the refraction of a plane wave from a denser to a rarer medium using Huygens' principle.

$A$ plane wavefront is incident on a water surface at an angle of incidence $60^{\circ}$. It then gets refracted at an angle of $45^{\circ}$. The ratio of the width of the incident wavefront to that of the refracted wavefront is $\left[\sin \frac{\pi}{4}=\cos \frac{\pi}{4}=\frac{1}{\sqrt{2}}, \sin 60^{\circ}=\frac{\sqrt{3}}{2}, \cos 60^{\circ}=\frac{1}{2}\right]$

What is the definition of a wavefront?