Wave Interactions

When waves bounce off barriers we call this reflection.  As waves reflect, the angle of reflection, which is measured between the outgoing path and the normal line perpendicular to the surface, is equal to the angle of incidence, which is measured between the incoming path and the normal line perpendicular to the surface.

When two waves interact in one medium, we call this interference.  They can interfere constructively, meaning the amplitude is larger than the individual waves, or they can interfere destructively, which reduces the amplitude of the combined wave.

When waves pass by the edge of a barrier, they undergo diffraction and spread out as if the edge of the barrier was a point source of waves.  This allows waves to curve and spread out as they pass around, through and past barriers.

When waves pass into a new medium, the frequency remains constant, but if the speed changes, so will the wavelength.  If a wave passes into a new medium at an angle to the boundary, it will change direction upon crossing into the new medium.  This is called refraction.  This phenomenon is responsible for objects appearing bent when they are partially submerged in water.