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: 15
Grade code: 2.2.2.LI.2
Strand code: 2
Sub-strand code: 2
Content standard code: 2.2.2.CS.1
Indicator code: 2.2.2.LI.2
Theme: ENERGY
Subtheme: WAVES
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This lesson introduces the fundamental concept of waves, which are all around us. A wave is essentially a disturbance that transfers energy from one place to another without a net transfer of matter. Understanding waves is crucial because they are the basis for how we see, hear, and communicate. From the ripples on the Keta Lagoon and the sound of the `atumpan` drum, to the radio waves that bring us Peace FM and the microwaves that power our mobile phones with MTN or Vodafone, waves are an integral part of our daily lives in Ghana. In this lesson, we will learn how to categorise these different types of waves based on their distinct properties.
This topic is all about sorting or classifying waves. We use three main "rules" or systems to do this. A single wave, like sound, can be classified using all three systems. System 1: Classification by Direction of Vibration
This system looks at how the particles of the medium (or fields, in some cases) move compared to the direction the wave's energy is travelling.
a) Transverse Waves Definition: A transverse wave is one in which the particles of the medium vibrate or oscillate perpendicular (at a 90° angle) to the direction of energy transfer (wave propagation). Visualisation: Imagine you and a friend are holding the ends of a long rope (`dada ba` rope). If you flick your wrist up and down, you will see a hump travel along the rope to your friend. The rope itself moves up and down, but the wave (the energy) moves forward. Vibration: Up and Down (Vertical) Energy Transfer: Forward (Horizontal) They are perpendicular. Key Features: They have crests (the highest points) and troughs (the lowest points). ``` Crest /\ / \ -----/----\-----/----\----- Direction of Energy ---> \ / \ / \ / \ / \/ Trough ``` Examples: Light waves and all other electromagnetic waves (radio, X-rays). Waves on a guitar string. Ripples on the surface of water (like in a ripple tank or at the beach).
b) Longitudinal Waves Definition: A longitudinal wave is one in which the particles of the medium vibrate or oscillate parallel to the direction of energy transfer. Visualisation: Imagine a Slinky spring. If you push one end forward, a "squash" travels down the spring. The coils of the spring move back and forth in the same direction that the energy is travelling. Vibration: Back and Forth (Horizontal) Energy Transfer: Forward (Horizontal) They are parallel. Key Features: They consist of areas where particles are close together, called compressions, and areas where they are spread apart, called rarefactions. ``` Direction of Energy ---> ||||| | | | ||||| | | | ||||| | | | C R R C R R C R R (C = Compression, R = Rarefaction) ``` Examples: Sound waves (This is the most important example!) Pressure waves, like a shockwave from an explosion. Ultrasound waves used in medical imaging.