Lesson Notes By Weeks and Term v4 - SHS 1
WAVES
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WAVES
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Subject: Physics
Class: SHS 1
Term: 2nd Term
Week: 2
Grade code: 1.2.2.LI.2
Strand code: 2
Sub-strand code: 2
Content standard code: 1.2.2.CS.2
Indicator code: 1.2.2.LI.2
Theme: ENERGY
Subtheme: WAVES
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This lesson explores the fascinating phenomenon of refraction—the bending of light. We see its effects every day without even realising it. Have you ever put a spoon in a glass of water and noticed it looks bent or broken at the water's surface? Or have you tried to pick up a stone from the bottom of a clear river, only to find it's deeper than it looked? These are not magic tricks; they are demonstrations of light waves changing direction as they move from one material (like air) to another (like water). Today, we will move beyond just observing this effect. We will learn how to quantify it by determining a special property of every transparent material called the refractive index.
2.1 What is Refraction?
Refraction is the bending of light (or any wave) as it passes from one medium to another medium of different optical density. Medium: A substance that light can travel through, e.g., air, water, glass, kerosene, diamond. Optical Density: A measure of how much a medium slows down light. A more optically dense medium (like glass) slows light down more than a less optically dense medium (like air). Note: This is different from physical density (mass/volume).
Why does light bend? Imagine you are pushing a lawnmower from a smooth pavement onto a thick, grassy lawn at an angle. The wheel that hits the grass first will slow down, while the other wheel on the pavement continues at the same speed. This difference in speed causes the entire lawnmower to pivot or turn. Light behaves in a similar way. Light travels at different speeds in different media. This change in speed causes it to bend.
Key Terms and Diagram: