“ a disturbance or variation that transfers energy progressively from point to point in a medium and that may take the form of an elastic deformation or of a variation of pressure, electric or magnetic intensity, electric potential, or temperature “ What is a Wave?

Wave = a disturbance or variation which travels through a medium

Vibrations and Wavesby Rifk i Irawan

the transfer of energy from one point to another.a wave :

WAVE

mechanical non - mechanical

require a medium for the transfer of energy to occur

do not require a medium for the transfer of energy to occur

Water waves Sound waves Electromagnetic waves (EM)

Types of Waves

Waves are divided into types according to the direction of the displacements in relation to the direction of the motion of the wave itself.

Longitudinal Waves

the displacement of the medium is parallel to the propagation of the wave

displacement

Velocity of propagation

Transverse Waves

the displacement of the medium is perpendicular to the direction of propagation of the wave

displacement

Velocity of propagation

compressions

rarefactions

Longitudinal Waves

λ

one wavelength

λ

one wavelength

amplitude

crest

trough

Transverse Waves

Longitudinal WavesTransverse WavesWater Waves

Terms used to describe wave motion

• The high points are called crests while the low points are called troughs.

• The amplitude is the maximum displacement from the rest position.• The wavelength (λ) is the distance between two successive crests or

two successive troughs.• The frequency ( f ) is the number of crests (or troughs) that pass a

point per second. The unit of frequency is Hertz ( Hz ).• The period ( T ) is the time taken to generate one complete wave.

• The speed ( v ) of the wave is the distance moved by a wave in one second.

T = 1 / f

v = λ / T v = f x λor

End of presentation

Exercise :

1. A vibration of frequency 5 Hz sends a wave of wavelength 0.8 m down a rope. What is the speed of the wave?

2. A wave of wavelength 1.5 m travels down a rope at a speed of 6 m s-1. What is the frequency of the wave?

3. The water waves below are traveling along the surface of the ocean at a speed of 2.5 m/s and splashing periodically against Wilbert's perch. Each adjacent crest is 5 meters apart. The crests splash Wilbert's feet upon reaching his perch. How much time passes between each successive drenching? Answer and explain using complete sentences.

1. What is the velocity of a wave of frequency 600 Hz and wavelength 0.5 m ?

2. What is the frequency of a wave of wavelength 0.9 m and velocity 300 ms-1 ?

3. What is the wavelength of a wave of velocity 300 ms-1 and frequency 1000 Hz ?

P Q9 cm

a. What is the wavelength of the waves shown in the figure above ?

b. The wave which is now at P reaches Q in 3 seconds. What is the speed of the wave ?

c. What is the frequency of the wave ?

1. A source of frequency 500 Hz emits waves of wavelength 0 .2 m. How long does it take the waves to travel 400 m ?

2. A wave of frequency 500 Hz travels between two points P and Q with a velocity of 300 ms-1 ? How many wavelengths are there in PQ if the length of PQ is 600 m!

3. A source of frequency 3 Hz generates waves with an amplitude of 0.5 cm and a wavelength of 12 cm. What is the velocity with which the waves travel across the surface ?