Lesson Notes By Weeks and Term v4 - SHS 2
WAVES
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WAVES
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Subject: Physics
Class: SHS 2
Term: 1st Term
Week: 19
Grade code: 2.2.2.LI.3
Strand code: 2
Sub-strand code: 2
Content standard code: 2.2.2.CS.2
Indicator code: 2.2.2.LI.3
Theme: ENERGY
Subtheme: WAVES
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This lesson explores two key aspects of waves: the phenomenon of echoes and the mathematical description of a progressive wave. We will first understand how sound waves reflect to create echoes, a principle used by bats for navigation and by fishermen on the Volta Lake or the Atlantic Ocean to measure water depth. We will then transition to the more abstract but powerful concept of the wave equation, which allows us to mathematically model and predict the behaviour of any travelling wave. Understanding these concepts is fundamental to fields like telecommunications, medicine, and geology.
This lesson is divided into two parts: Echoes and The Progressive Wave Equation. Part A: Echoes and Their Application What is an Echo?
An echo is a reflection of sound that arrives at the listener with a delay after the direct sound. For an echo to be heard distinctly, the time delay between the original sound and the reflected sound must be at least 0.1 seconds. This is because the human ear cannot distinguish between two sounds if they arrive within this time interval.
The formation of an echo is a simple process: A sound wave is produced from a source. The wave travels through a medium (like air or water). It strikes a hard, flat surface (like a cliff, a building wall, or the seabed). The wave is reflected from the surface. The reflected wave travels back to the source/listener. The Mathematics of Echoes
We can use the basic relationship between speed, distance, and time to analyze echoes. Speed (v) = Total Distance Travelled (D) / Total Time Taken (t)