Lesson 2 Wave Motion

The role of waves in energy transfer When the first domino piece falls, its energy would transfer to the next one. That falls down in turn, transferring the energy to the next piece and so on. Energy transfer through the domino pieces continues and the pieces never change position in the line. Note

Wave It is the disturbance that propagate and transfer energy in the direction of propagation.

The concept of wave motion When the tuning fork vibrates, the produced energy is transferred in the form of sound waves.

The concept of wave motion The particles of the medium (air and smoke particles) do not move form their original places during transferring sound waves carrying energy to the candle flame.

Wave motion. It is the movement resulting from the vibration of the medium particles at a certain moment in a specific direction

Types of waves

According to the direction of vibration of medium particles relative to the direction of propagation Transverse waves Longitudinal waves

According to the ability to propagate and transfer energy Mechanical waves Electromagnetic waves

Compare between Transverse waves and Longitudinal waves.

Transverse waves Longitudinal waves

Transverse waves Longitudinal waves

Note During wave propagation, the particles of the medium do not change position; however they vibrate around their point of rest.

Application Physiotherapy tubs (Jacuzzi)

Compare between Electromagnetic waves and Mechanical waves.

Electromagnetic waves 1- Don’t need media to travel through. 2- Fast (3 X 10 8 )m/s 3- Transverse wave only. Ex.: Light waves Radio waves.

Mechhanical waves 1- Need media to travel through. 2- Slow.(compared to electromagnetic waves).

Concepts related to wave motion 1- Wavelength. (λ) 2- Amplitude. 3- Wave velocity.(v) 4- Frequency.(F)

1- Wavelength (λ) It is the distance between the centers of two consecutive compression or rarefaction. OR It is the distance between the centers of two consecutive crests or troughs.

2- Amplitude It is the maximum displacement achieved by the particles of the medium away from their points of rest.

wave velocity(v) = distance covered by the wave in meters(m) time in seconds(s) 3- Wave velocity(v) It is the distance covered by the wave in one second. Wave velocity= Frequency X Wavelength v = F X λ

3- Wave velocity(v)

Air 340 m/s Water 1500 m/s Wood 1850 m/s Note The velocity of a given wave is constant as it travels through the same medium. However, it differs as the nature of the medium changes Wave velocity represents the velocity of the transfer of the energy carried by the wave.

4- Frequency (F) It is the number of waves made in one second. F X Periodic time= 1

Wave velocity= Frequency X Wavelength v = F X λ The law of wave propagation: