Which of the following wave motions may be used to demonstrate the phenomenon of polarisation?

Question 22

Which of the following wave motions may be used to demonstrate the phenomenon of polarisation?

A a sound wave from a thunderclap

B a surface wave in a water ripple tank

C a stationary wave in an organ pipe

D a stationary wave on a stretched wire

Reference: Past Exam Paper – November 2015 Paper 12 Q25

Solution:

Answer: D. 

Polarisation cannot occur with a longitudinal wave as the direction of vibration is parallel to the direction of motion of the wave. Since sound is longitudinal, it cannot be used to demonstrate polarisation. [A incorrect]

If the movement of a wave is horizontal, after polarisation, the movement would be vertical. Surface waves on water demonstrate interference and diffraction easily but do not easily show polarisation. [B incorrect]

The movement of a wire can be horizontal or vertical (or a combination of the two). So, it can easily be used to demonstrate polarisation. [D is correct]