WAVES  
Wave  
:
Is a progressive disturbance propagated from a point in a medium (matter)  
on space without the movement of the points themselves.  
OR  
Is a periodic disturbance that transfers energy from one point to another  
For example, light  
,
sound and water waves  
Terms Used  
1. Period: Is the time taken by the wave to repeat itself.  
OR  
Is the time taken for the wave to complete one cycle.  
It is represented by letter T. Its SI unit is second (s)  
2. Amplitude: Is the maximum displacement of the wave from the equilibrium position.  
It is represented by letter  
A
. Its SI unit is meter (m).  
3. Crest:  
Is the point of maximum positive displacement of the wave from  
the equilibrium position  
4. Trough:  
Is the point of maximum negative displacement of the wave from  
the equilibrium position  
5. Wavelength  
:
Is the distance between two successive or adjacent crest troughs.  
OR  
Is the distance travelled by the wave to complete one cycle  
It represented by letter Lambda (λ)  
6. Frequency: Is the number of crests or troughs that pass a given point per unit time.  
OR  
Is the number of cycles per unit time.  
It is represented by letter  
f
. Its SI unit is hertz (Hz).  
1hertz (Hz) = 1per second (s-1)  
Then 풇 = ퟏ  
, where T is a periodic time  
푻
7. Wave velocity: Is the speed at which the wave moves through a medium  
OR  
Is the displacement of the wave per unit time.  
It is represented by letter  
v
Mathematically  
ퟏ
푻
풘풂풗풆풍풆풏품풕풉  
풕풊풎풆  
흀
= 흀 ×  
= 흀 × 풇  
( )  
풔풑풆풆풅 푽 =  
=
푻
Therefore: 풗 = 흀 풇  
Examples:  
1. Sound waves have a frequency of 16 kHz. What is the periodic time for the  
waves?  
Soln:  
Given:풇 = ퟏퟔ풌푯풛 = ퟏퟔ ퟎퟎퟎ푯풛  
ퟏ
푰
ퟏ
From 풇 =  
:
=
→ 푻 =  
= ퟎ. ퟎퟎퟎퟎퟔퟐퟓ 풔  
풇
ퟏퟔퟎퟎퟎ  
푻
2. A radio station transmits waves at a frequency of 95.6 MHz. What is the  
wavelength of the waves transmitted? (c = 3.0 x 108 m/s)  
Soln:  
Given: 풇 = ퟗퟓ. ퟔ푴푯풛 = ퟗퟓ. ퟔ 풙 ퟏퟎퟔ 푯풛, c = 3.0 x 108 m/s  
ퟖ
풗
ퟑ.ퟎ 풙ퟏퟎ  
From:  
풗 = 흀 풇  
→ 흀 = 풇 =  
= ퟑ.ퟏퟒ 풎  
ퟔ
ퟗퟓ.ퟔ 풙 ퟏퟎ  
Class Activity  
1. From the diagram below, determine the amplitude, period and frequency of the  
wave  
ANS: Amplitude, A = 0.5m  
Period, T = 0.2  
Frequency = 5Hz  
2. From the diagram below, determine the wavelength and velocity of the wave,  
frequency of the wave is 5Hz  
(
ANS V = 10m/s)  
3. What is the amplitude and wave length of the wave in the diagram below?  
ANS: A = 0.03m, Wavelength = 0.08 m  
4. The distance between successive crests of water ripples in a ripple tank  
experiment is 3.2 cm and their wave speed is 26 cm/s. Determine the  
wavelength, Frequency and period of the ripples ANS: f = 8.125 Hz, λ=3.2cm T=0.123  
Hz  
Types of waves  
•
•
Electromagnetic wave  
Mechanical wave  
Electromagnetic Wave:  
•
Is the type of wave which does not require a medium to transfer energy.  
Mechanical Wave:  
•
Is the type of waves in which a medium is required to transfer energy.  
Difference between Mechanical and Electromagnetic Waves  
Mechanical waves  
Electromagnetic waves  
❖
Are disturbances which are  
❖
Are disturbances made up of  
transported through a medium due to  
particle to particle interaction  
Requires a material medium to  
transfer energy  
Cannot travel through vacuum  
Examples are water waves, sound  
waves etc  
electric and magnetic fields  
❖
❖
Do not requires materials  
medium to transfer energy  
Can travel through vacuum  
Examples are X – rays, Visible  
light etc  
❖
❖
❖
❖
Types of Wave motion  
➢
➢
Transverse wave  
Longitudinal wave  
Transverse Wave  
•
I
s the mechanical wave in which particles of the medium vibrate in a direction  
perpendicular to the direction of movement of the wave.  
For example, water wave  
This wave enables a duck in a lake floating in the same position as the wave  
•
•
passes (This is due to the vertical displacement of water waves ie transversely  
)
Diagram  
:
•
This vibration of medium causes a boat on the ocean moves up and down while  
the waves themselves move toward the shore  
Longitudinal Wave  
•
Is the mechanical wave in which particles of the medium vibrate in a direction  
parallel to the direction of movement of the wave.  
•
•
•
For example, sound wave  
It consists of compressions and rarefactions  
Compression: Is a region in a longitudinal wave where the particles are  
closest together  
•
R
arefactions: Is a region in a longitudinal wave where the particles are  
furthest apart  
Differences between Transverse wave and Longitudinal waves  
Transverse wave  
Longitudinal wave  
The particles of the medium vibrate in the  
same direction in which the wave advance  
It is formed of a series of compressions  
and rarefactions  
Particles of the medium vibrate perpendicular  
to the direction in which the wave advances  
It is formed of crests and troughs  
It can propagate only in solids and at the  
surface of liquids  
There is no pressure variations  
It can propagate in all types of media  
(solid, liquid and gas)  
The pressure and density are maximum at  
compressions and minimum at rarefactions  
Examples are:  
Examples are:  
•
Ripples produced on the surface of  
water when stone is dropped into it  
•
•
•
Sound waves travel through air  
Waves in a coil (helical) spring  
Vibrations of air column in organ  
pipes  
•
Waves produced in a rope fixed at  
one end when the free end is  
moved up and down rapidly  
Waves in the stretched strings  
Earthquake S waves  
•
Earthquake P waves  
•
•
Properties of Waves  
➢
➢
➢
➢
Reflection of waves  
Refraction of waves  
Interference of waves  
Diffraction of waves