Lesson Notes By Weeks and Term v4 - SHS 1
POWERING THE FUTURE WITH ENERGY FORMS
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POWERING THE FUTURE WITH ENERGY FORMS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: General Science
Class: SHS 1
Term: 2nd Term
Week: 12
Grade code: 3.3.1.LI.2
Strand code: 3
Sub-strand code: 1
Content standard code: 3.3.1.CS.1
Indicator code: 3.3.1.LI.2
Theme: VIGOUR BEHIND LIFE
Subtheme: POWERING THE FUTURE WITH ENERGY FORMS
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Light is a form of energy that is all around us. From the sun that helps our crops grow to the screen of the phone you use, we depend on light every second. But have we ever wondered how we can control this light energy? How do spectacles (glasses) help people see clearly? How does the internet signal travel at incredible speeds from Accra to Tamale through tiny glass cables? The answer lies in understanding mirrors and lenses. This lesson will explore the fascinating world of how light behaves when it interacts with these tools.
This section breaks down the core scientific principles you need to teach. A. Refraction and Refractive Index
When you put a spoon in a glass of water, it looks bent. This is not magic; it is a phenomenon called refraction. Definition: Refraction is the bending of light as it passes from one medium (like air) to another medium (like water or glass) of different optical density. Why it happens: Light travels at different speeds in different materials. It travels fastest in a vacuum (and very fast in air) and slows down in denser materials like water or glass. This change in speed causes the light ray to bend. Analogy: Imagine pushing a shopping trolley from a smooth tiled floor onto a thick, grassy area at an angle. The wheel that hits the grass first will slow down, while the other wheel continues at the same speed, causing the trolley to turn. Light behaves in a similar way.
Refractive Index (n) This is a number that tells us *how much* a material can bend light. Definition: The refractive index (n) of a medium is the ratio of the speed of light in a vacuum (c) to the speed of light in that medium (v). Formula: `n = c / v` Where `c` (speed of light in vacuum) is approximately 3.0 x 10⁸ m/s. Key Idea: A higher refractive index means the material is optically denser, and light travels slower in it, causing more bending. Refractive index of Air ≈ 1.00 Refractive index of Water ≈ 1.33 Refractive index of Glass ≈ 1.50 B. Snell's Law
Snell's Law is the formula that allows us to calculate exactly how much light will bend. The Setup: When a ray of light hits the boundary between two media, we measure angles from a line called the normal (a line drawn perpendicular, or at 90°, to the surface). Angle of Incidence (θ₁): The angle between the incoming light ray and the normal. Angle of Refraction (θ₂): The angle between the bent light ray (in the new medium) and the normal. Snell's Law Formula: `n₁ sin(θ₁) = n₂ sin(θ₂)` `n₁` = refractive index of the first medium (where light is coming from). `θ₁` = angle of incidence. `n₂` = refractive index of the second medium (where light is going to). `θ₂` = angle of refraction.