Question

electromagnetic waves can reflects .....how???

Answer 1

Electromagnetic waves can reflect, because they follow the Fermat's principle, that they take the path of least time. When a ray approaches an opaque medium which it can not enter, then it either gets absorbed or gets reflected. For non-shiny and dark media like coal, it absorbs the rays. For shiny media like opaque ground glass and the surfaces of most metals, it reflects the rays.

Answer 2

   Electromagnetic waves are consisting of oscillating electric (electrostatic) and magnetic fields perpendicular to the direction of propagation.

   These fields touch the atoms and molecules of the material on which they are incident.  These atoms and molecules have some energy levels.  They can absorb certain quantities of energy of certain frequencies.  That depends on the structure of that element or elements inside the substance.

   Due to attractive forces between the electric/magnetic fields of matter (atoms/molecules) inside the substance, some waves are absorbed.  Some part of the waves is not absorbed and hence it is reflected back in to the incident medium.  It is possible that the material absorbs certain energy and then releases it back again after a little while.

   The reflection and absorption follow certain principles.

   You see the rebounding of a ball when it hits a wall.  It is similar phenomenon.  Some waves get reflected and their electric and magnetic fields change direction and phase.