Lesson Notes By Weeks and Term v4 - JHS 1
ENERGY
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ENERGY
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Subject: Science
Class: JHS 1
Term: 2nd Term
Week: 8
Grade code: B7.4.1.3.1
Strand code: 4
Sub-strand code: 1
Content standard code: B7.4.1.3
Indicator code: B7.4.1.3.1
Theme: FORCES AND ENERGY
Subtheme: ENERGY
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Light is a form of energy that helps us to see and do many activities in Ghana—reading at night, using torchlight during “dumsor”, crossing roads safely, taking photos with phones, and even using solar panels. To use light well and to stay safe (e.g., avoiding eye damage from direct sunlight), learners must understand an important property of light: light travels in a straight line (in a uniform medium like air). This lesson is aligned to NaCCA Indicator B7.4.1.3.1: Demonstrate how light travels in a straight line through simple experiments and clear explanations.
2.1 What is Light (as Energy)? Light is a form of energy that travels from a source (like the Sun, a bulb, a candle, a torch) to our eyes. Light makes vision possible and can also transfer energy (e.g., sunlight warming surfaces). 2.2 Light Rays and Straight-line Travel A ray is an imaginary straight line that shows the direction in which light travels. In a uniform medium (same material throughout, like still air), light travels in straight lines. This is why we can represent light using straight ray diagrams.
Important note (for understanding): Light can change direction when it meets a new medium (like air to water/glass) — that is refraction. Light can bounce off surfaces — that is reflection. But the indicator for this lesson focuses on proving that before it meets a new medium or surface, it travels straight. 2.3 Evidence: Shadows A shadow forms when an object blocks light.
Why shadows show straight-line travel: If light could bend around objects easily, shadows would not be sharp. Because light travels straight, the region behind an opaque object receives little or no light, forming a shadow.
Types of objects and shadows Opaque (e.g., wood, book, stone): blocks most light → dark shadow. Translucent (e.g., frosted glass, thin cloth): blocks some light → faint shadow. Transparent (e.g., clear glass, clean water): allows most light → very faint/no shadow. 2.4 Simple Ray Diagram Explanation (Step-by-step) Example: Torch shining on a book to form a shadow on a wall. Draw the torch (light source). Draw straight rays from the torch to the book. Rays that hit the book are blocked. Rays that pass around the book reach the wall. The region on the wall where rays cannot reach becomes the shadow.