M. Manser (2014)

Module P1:  Waves, the wave equation and calculations M. Manser Sackville School

Examples of include…. Water waves, Light waves, IR, microwaves, UV. S-waves in an earthquake. In a transverse wave, the particles vibrate at right angles to the direction of travel of the wave In a longitudinal wave, the particles vibrate in the same direction as the direction in which the energy is transferred. Examples of include…. sound waves, P-waves in an earthquake. M. Manser Sackville School

Rest position of particle  wavelength a The distance between two adjacent crests or troughs is the wavelength ( ) and is measured in metres (m) The maximum disturbance caused by a wave is the amplitude (a) and is measured in metres (m). These three points are “in phase” with each other M. Manser Sackville School

The frequency is the number of waves passing any point each second. frequency = number of waves past a point / time frequency is measured in hertz (Hz) 1 wave per second = 1 Hz If this set of transverse waves pass a point in one second, what is the frequency? 4 Hz Frequency of transverse waves

Frequency of waves – activity

These waves are travelling across the surface of a pond. The length of each wave is 0.25 m. From this example, the connection between speed, frequency and wavelength is: How is wave speed calculated? speed = frequency x wavelength 0.5 m/s = 2 Hz x 0.25 m This means that the waves travel 0.5 m each second, so the speed of the waves is 0.5 m/s. Two waves pass the duck each second, so the frequency is 2 Hz.

Wave speed is measured in metres per second (m/s). What is the formula for wave speed? For any set of waves, the wave speed (v) can be calculated from the frequency (f) and wavelength ( ) using this formula: What are the units of speed, frequency and wavelength? Frequency is measured in hertz (Hz). Wavelength is measured in metres (m). wave speed = frequency x wavelength v = f x

  x A formula triangle helps you to rearrange a formula. The formula triangle for wave speed (v), frequency (f) and wavelength ( ) is shown below. Cover the quantity that you are trying to work out, which gives the rearranged formula needed for the calculation. So to find frequency (f), cover up f… …which gives the formula… f = v

Wave speed problems

The two pink particles are in phase with each other. They are always the same distance from the rest position, and are always moving in the same direction. They are one wavelength apart. Also look at the dark blue, green and yellow particles. Particles which are completely out of phase will always be doing the exact opposite of each other. For example, the particle at a peak is out of phase with one at a trough. These particles are ½ of a wavelength apart. M. Manser Sackville School

amplitude – The maximum distance any point in a wave moves from its rest position. compression – A stretched-out section of a longitudinal wave. frequency – The number of waves passing a point each second. It is measured in hertz (Hz). longitudinal wave – A type of wave in which the particles vibrate back and forth, which is parallel to the wave direction, e.g. sound and P waves. rarefaction – A bunched-up section of a longitudinal wave. transverse wave – A type of wave in which the particles vibrate up and down, which is at right angles to the wave direction, e.g. electromagnetic, water and S waves. wavelength – The distance between two adjacent crests. Glossary

Multiple-choice quiz