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: 16
Grade code: 2.2.2.LI.4
Strand code: 2
Sub-strand code: 2
Content standard code: 2.2.2.CS.1
Indicator code: 2.2.2.LI.4
Theme: ENERGY
Subtheme: WAVES
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Sound is a fundamental part of our lives in Ghana. From the vibrant rhythms of Adowa and Kpanlogo music to the call to prayer, the bustling noise of Makola market, and simple conversations with our families, we are surrounded by sound waves. But have you ever wondered how fast these sounds travel from the source to our ears? In this lesson, we will explore two scientific methods to measure this speed: one using simple echoes, like shouting across a field, and another, more precise method using the fascinating phenomenon of resonance, which is the same principle that makes a flute or a xylophone produce its unique notes.
This lesson is divided into two main parts, each focusing on a different method to determine the speed of sound. Part A: Determining the Speed of Sound using Reflection (Echo Method) What is Reflection of Sound? Just like light bounces off a mirror, sound waves bounce off hard, flat surfaces. This bouncing back of sound waves from a surface is called reflection of sound. An Echo is a reflected sound that is heard distinctly after the original sound. Condition for hearing an echo: For the human ear to distinguish between the original sound and its reflection, there must be a time interval of at least 0.1 seconds between them. The Echo Formula Imagine you are standing a distance, `d`, from a tall wall (e.g., the wall of the Assembly Hall). You clap your hands. The sound travels to the wall. This is distance `d`. The sound reflects off the wall and travels back to your ears. This is another distance `d`. The total distance the sound travels is `d + d = 2d`.
We know the basic formula for speed: `Speed = Total Distance / Time Taken`
In this case, the time taken, `t`, is the time from when you clap to when you hear the echo. So, the speed of sound, `v`, can be calculated as:
`v = 2d / t`