Lesson Notes By Weeks and Term v4 - SHS 2
WAVES
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
WAVES
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Physics
Class: SHS 2
Term: 1st Term
Week: 15
Grade code: 2.2.2.LI.3
Strand code: 2
Sub-strand code: 2
Content standard code: 2.2.2.CS.1
Indicator code: 2.2.2.LI.3
Theme: ENERGY
Subtheme: WAVES
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
This lesson introduces the fundamental properties of waves. Waves are all around us and are the primary way energy moves from one place to another. In Ghana, we experience waves every day: the sound from a beating *atumpan* drum, the ripples in the water at Labadi Beach, the radio waves that bring us programs from Joy FM or Peace FM, and the light from the sun that helps our crops grow. Understanding the language used to describe waves—amplitude, wavelength, frequency, period, and velocity—is the first step to understanding these powerful phenomena and how they shape our world and technology.
2.1 What is a Wave? A wave is a disturbance that travels through a medium (like water or air) or space, transferring energy from one point to another without causing a permanent displacement of the medium itself. Think of a "stadium wave" made by people. The wave travels around the stadium, but each person just stands up and sits down in their own spot. The energy moves, but the people (the medium) do not. 2.2 Visualising a Wave: The Sinusoidal Graph We can represent a simple wave using a sinusoidal graph. This graph helps us to visualise and measure its properties. There are two main types of graphs we use: Displacement-Distance Graph: This is a "snapshot" of the wave at a single moment in time. It shows the displacement of all particles of the medium at different positions. Displacement-Time Graph: This graph follows a single particle in the medium and shows how its displacement changes over time.
Let's look at the key properties using these graphs.
(A) Displacement-Distance Graph Imagine a wave frozen in time. Amplitude (A): Definition: The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. In simpler terms, it's the "height" of a crest or the "depth" of a trough from the centre line. Unit: Metre (m). On the graph: The distance from the horizontal axis (equilibrium) to the top of a crest or the bottom of a trough. Meaning: For a water wave, amplitude is related to the height of the wave. For a sound wave, it's related to the loudness. For a light wave, it's related to the brightness. Wavelength (λ - Greek letter 'lambda'): Definition: The distance between two consecutive corresponding points on a wave. The easiest points to use are two consecutive crests or two consecutive troughs. It is the length of one complete wave cycle. Unit: Metre (m). On the graph: The horizontal distance from one crest to the next crest.
(B) Displacement-Time Graph Now, let's focus on one point in the water and watch it move up and down over time. Period (T): Definition: The time taken to complete one full oscillation or one full wave cycle. Unit: Second (s). On the graph: The time taken for the wave to go from one crest to the next consecutive crest. Frequency (f): Definition: The number of complete oscillations or cycles produced per second. Unit: Hertz (Hz). 1 Hz means one cycle per second. Relationship to Period: Frequency and Period are inverses of each other. If a wave takes a long time for one cycle (high period), it means fewer cycles will happen each second (low frequency). Formula: `f = 1 / T` or `T = 1 / f` Meaning: For sound, frequency determines the pitch (high frequency = high pitch, like a whistle; low frequency = low pitch, like a bass drum). For light, frequency determines the colour. 2.3 The Wave Equation: Connecting Speed, Wavelength and Frequency This is the most important relationship in our study of waves. Let's derive it together, just as the curriculum suggests.