Stationary Waves

Page 1

Progressive Waves Reflected at a Boundary Can Create a Stationary Wave

A stationary or standing wave is the superposition of two progressive waves

with the same frequency (wavelength) moving in opposite directions.

No energy is transmitted by

stationary wave

For most frequencies the

resultant pattern is difficult to detect. However, if the the oscillator

happens to produce an exact number of waves in the time it takes to get a

wave to the boundary and back to the starting point, the original and

reflected waves reinforce eachother

At these resonant

frequencies, a stationary wave occurs, where the pattern remains unmoved.

Stationary Waves in

Strings Form Oscillating Loops Separated by Nodes

Each particle vibrates at right

angles to the string. Nodes are where the amplitude of the vibration is zero.

Anti nodes are points of maximum amplitude. At resonant frequencies, an exact

number of half wavelengths fits onto the string.

Stationary waves

can be demonstrated with microwaves and sounds

Page 2

Factors Affecting Resonant Frequencies of A

String Can Be Investigated

The following conclusions can be drawn from the experiment:

1. The longer the string, the lower the resonant frequency

2. The heavier the string (i.e. the more mass per unit length), the lower the resonant frequency. For a given length, a lower wave speed, c, makes a lower frequency, f.

3. The looser the string, the lower the resonant frequency