Waves and Oscillations - Wave Motion : Standing Waves

When two waves of same frequency and amplitude travel in opposite directions at same speed,their superposition gives rise to a new type of waves called stationary waves or standing waves. The equation of these standing waves has been obtained and their important characteristics have been discussed. The formation of nodes and antinodes is the most common feature of a standing wave. The nodes divide the medium into loops. All the particles in a loop vibrate in same phase,but in opposite phase with the particles in the adjacent loop. As in a stationary wave nodes are permanently at rest so no energy can be transmitted from one loop to another,hence the name stationary wave. The extent to which the resulting wave is standing is measured in terms of a parameter called Standing Wave Ratio. The minimum value of SWR is one for a Progressive Wave and its maximum value is infinite for a perfect standing wave. The value of SWR for all other waves lie between one and infinity.