# STATIONARY WAVES: Part 3STATIONARY WAVES: Part 3

1. Stationary Wave: A stationary/standing wave is the superposition of two progressive waves
with the same wavelength, moving in opposite directions.
2. As the waves, of the same wavelength and frequency meet at a point, the points where they
interfere destructively are called nodes. These points do not move at all. At other points, the
waves interfere constructively and form antinodes. These are points of greatest amplitude
and therefore intensity.
3. Node: A node occurs where the amplitude is (always) zero
4. Antinode: An antinode occurs where the amplitude (of the standing wave) takes the
maximum (possible) value.
5. The separation between two adjacent nodes (or antinode) is equal to half the wavelength of
the original progressive wave – to work out the wavelength of the original progressive wave
you must double this distance. The frequency of the standing wave is the same as the
progressive wave that formed.
6. Demonstrating standing waves on a string:
a. You can demonstrate stationary waves by attaching a vibration transducer at one
end of a stretched string with the other fixed. The transducer is given a wave
frequency by a signal generator and creates that wave by vibrating a string.
b. The wave generated by the vibration transducer is reflected back and forth.
c. For most frequencies the resultant pattern is a jumble. However, at certain
‘’resonant’’ frequencies you get a stationary wave where the pattern doesn’t move.
d. At resonant frequencies, an exact number of half wavelengths fits onto the string.
e. A transverse stationary wave forms on the string.
f. Fundamental Mode of Vibration (Frequency): The lowest frequency in a harmonic
series where a stationary wave forms. Only one ‘loop’ forms. This is called f0