Does light bends when it comes in contact with magnet?
Path of light is unaffected by presence of external magnetic field.
1.
What determines the shape of wavefront?
The shape of a wavefront is determined by two factors:
a) Shape of source
b) Distance from source
A point source produces spherical wavefronts.
Similarly, a linear source will produce cylindrical wavefronts.
If the source is at an infinite distance, the observer will observe plane wavefronts.