Stationary waves

Question 1

Define Stationary Waves

Answer 1

1) Stationary waves is a disturbance in the medium where vibrational energy is stored rather than transferred
2) It is formed by 2 interference of two progressive waves of the same kind, same amplitude, same speed, and traveling along the same line in the opposite direction.

Question 2

Conditions required for formation of stationary waves

Answer 2

1) Two progressive waves must interfere with similar amplitude, same frequency/wavelength of speed or simply coherent, same type, moving in the opposite direction and interfere at a point
2) For transverse waves, the waves are either UNPOLARISED or share the same axis of polarisation

Question 3

Define nodes

Answer 3

Nodes are points on stationary waves where the amplitude of vibration is zero or minimum

Question 4

Define Antinodes

Answer 4

Antinodes are points on stationary waves where the amplitude of vibration is maximum

Question 5

Distinguish the difference between progressive waves and stationary waves.

Answer 5

For progressive waves, phase is different for all points within one wavelength. For stationary waves, phase is the same for all points WITHIN a nodal loop but anti-phase for a point in one nodal loop and another point from an adjacent loop.

Energy is stored and not transported in stationary waves, where progressive waves transport energy from ONE POINT TO ANOTHER

For stationary waves, the amplitude of vibration varies from the maximum at antinodes to minimum at nodes while the amplitude is the same at all points of the waves

Question 6

End correction of pipes..why do we do that?

Answer 6

Experimental evidence suggests that the anti-nodes occur slightly beyond the end of the pipe. This small extension, e must be added to the length of pipe to determine is wavelength of sound wave

Question 7

Stationary longitudinal wave e.g. sound wave in a pipe

how is it generated

Answer 7

1) Sound from the open end travels along the pipe and reflects at the closed end.
2) The reflected wave overlaps/interferes at the incident waves
3) At some specific frequencies, a loud sound is heard
4) At a closed end. The reflected wave is 180 out of phas with incident wave The incident and reflected waves always CANCEL out here and so, a displacement node is formed
5) At certain points along the pipe, 2 waves meet in phase, resulting in constructive interference. The amplitude is Max
6) At some other points, two waves meet antiphase, resulting in destructive interference. Amplitude is minimum or 0.