The diagram shows a transverse wave - Leaving Cert Physics - Question c - 2014

Frequency ( $f$ ) is defined as the number of waves passing a given point per unit time. In this case, 20 waves pass a point every second, therefore the frequency is:

$f = 20 \, \text{Hz}$

To calculate the velocity ( $v$ ) of the wave, we can use the formula:

$v = f \cdot \lambda$

Where:

• $f = 20 \, \text{Hz}$ (the frequency calculated)
• $\lambda = 1.5 \, \text{m}$ (the distance A)

Substituting in the values gives:

$v = 20 \, \text{Hz} \cdot 1.5 \,\text{m} = 30 \, \text{m/s}$

Longitudinal waves cannot be polarised. A common example of a longitudinal wave is sound or pressure waves, which propagate through a medium by compressing and rarefying regions of the medium.