Lesson Notes By Weeks and Term v4 - SHS 2
WAVES
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WAVES
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Physics
Class: SHS 2
Term: 1st Term
Week: 19
Grade code: 2.2.2.LI.2
Strand code: 2
Sub-strand code: 2
Content standard code: 2.2.2.CS.2
Indicator code: 2.2.2.LI.2
Theme: ENERGY
Subtheme: WAVES
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This lesson introduces the classification of sound waves based on their frequency. In our daily lives in Ghana, we are surrounded by sounds—from the vibrant rhythms of Highlife and Afrobeats music, the calls of sellers in the Makola market, to the sounds of drumming and the engines of tro-tros. However, the world of sound is much wider than what our ears can perceive. This lesson explores the full spectrum of sound, including the low-frequency sounds used by elephants and the high-frequency sounds used in medical technology, helping us understand the invisible waves that shape our world.
2.1. What is Sound and Frequency? Sound is a form of energy that travels as a longitudinal wave. It is a mechanical wave, which means it requires a medium (like air, water, or solids) to travel. It cannot travel through a vacuum. Frequency (f) is the most important property for classifying sound. It is defined as the number of complete vibrations or cycles a wave makes in one second. The standard unit for frequency is the Hertz (Hz). 1 Hz = 1 vibration per second. 1,000 Hz = 1 kilohertz (kHz). 1,000,000 Hz = 1 megahertz (MHz).
Think of a drummer. If they hit the drum slowly, say once every second, the frequency is 1 Hz. If they perform a fast drumroll, hitting it 50 times in a second, the frequency is 50 Hz. In sound, higher frequency corresponds to a higher *pitch* (like a whistle), and lower frequency corresponds to a lower *pitch* (like a deep bass drum). 2.2. The Spectrum of Sound
The entire range of sound frequencies can be divided into three main categories based on the limits of human hearing. The average young, healthy human can hear frequencies from 20 Hz to 20,000 Hz (or 20 kHz).
Visual Representation of the Sound Spectrum: