JSS 3: WAVE

A wave is a disturbance that transfers energy from one point to another without transferring matter.

Types of Waves

There are two major types of waves, namely:

(a) Mechanic waves

(b) Electromagnetic waves

(a) Mechanical Waves

A wave that requires a medium to travel through (e.g., water, air, solids).

Examples of mechanical Waves: Sound waves, water waves, seismic waves.

Types of mechanical Waves

(i) Transverse waves

(ii) Longitudinal waves

Transverse Waves: In Transverse waves, the particles move perpendicular to the direction of wave propagation (e.g., water waves, light waves).

Longitudinal Waves: The particles move parallel to the direction of wave propagation (e.g., sound waves).

(b) Electromagnetic Waves

They are waves that do not require a medium to travel. They can move through a vacuum.

Examples: Light, radio waves, X-rays, microwaves etc

Wave Parameters

(i) Crest - The highest point on a wave

(ii) Trough - The lowest point on a wave

(iii) Wavelength (λ): The distance between two successive crests or troughs. It is measured in meters (m)

(iv) Frequency (f): The number of wave cycles passing a point per second. It is measured in Hertz (Hz).

(v) Period (T): The time taken for one complete wave cycle (T = 1/f).

(vi) Amplitude: The maximum displacement of particles from the rest position.

(vii) Wave Speed (v): The speed at which the wave propagates. It is given by the formula:

v = f x λ

Properties of Waves

(a) Reflection: Bouncing back of waves when they hit a barrier (e.g., echoes).

(b) Refraction: Bending of waves as they pass from one medium to another.

(c) Diffraction: The spreading out of waves when they pass through an opening or around obstacles.

(d) Interference: When two or more waves meet:

Types of interference

(i) Constructive Interference: When waves combine to form a larger amplitude.

(ii) Destructive Interference: When waves cancel each other out.

Applications of Waves

(i) Sound waves is used for Communication and in sonar.

(ii) Light waves is used for Vision and in optical fibers.

(iii) Microwaves is used for Cooking and in satellite communication.

(iv) Radio waves is used for Broadcasting and in wireless communication.

Calculations:

Example 1: What is the wavelength of the sound from a tuning fork that vibrates at a frequency of 300Hz in air? (velocity of sound = 330m/s)

Solution:

Speed of sound =Frequency x wavelength 

                          V= f x λ

                     330 = 300 x λ

                         λ = 330/300 

                         λ = 1.1 m 

Example 2: A source of sound produces waves in air of wavelength 1.5m. If the speed of sound in air is 330m/s. Find the frequency of the vibration 

Solution:

Speed of sound =Frequency x wavelength 

                          V= f x λ

                     330 = f x 1.5 

                          f = 330/1.5 

                          f = 220Hz