Force applied causes
deformation in the object. It changes the relative positions of
constituent particles in the crystal lattice.
As soon as that happens, the interatomic or intermolecular forces come
into play and they, tend to restore the solid back to it's original
shape.
This restoring force per unit area is called Stress . When external forces are removed, the internal forces tend to restore the solid back.
This property is called Elasticity .
However, no material is perfectly elastic and what happens is that, the body is not able to restore itself completely.
Force, newtons 3rd law of motion stated for every action there is an equal and opposite reaction
Nothing happens to the mirror.
However, if the ray is within some suitable range of
wavelengths, the ray is reflected from the mirror's surface.
