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: 14
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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This lesson explores the fascinating world of light energy and how we control it using mirrors and lenses. Light is all around us, from the sun that helps our crops grow to the screen of our phones. Understanding how light behaves when it hits different materials is fundamental to many technologies that shape our modern Ghanaian life. We will investigate how mirrors in our homes and on our cars work, why eyeglasses can help people see clearly, and how the same principles allow for super-fast internet through fibre optic cables.
This section covers the core scientific principles needed to understand the indicator. We will move from the basic behaviour of light to the laws that govern it and the technologies that use it. A. Reflection of Light and Mirrors
Reflection is the bouncing back of light when it strikes a surface. A smooth, shiny surface like a mirror reflects light very well. Laws of Reflection: The angle of incidence (angle between the incoming ray and the normal) is equal to the angle of reflection (angle between the reflected ray and the normal). The incident ray, the reflected ray, and the normal at the point of incidence all lie in the same plane. Types of Mirrors: Plane Mirror: A flat mirror. It forms an image that is virtual (cannot be caught on a screen), erect (upright), the same size as the object, and laterally inverted (left and right are swapped). *Example:* Bathroom mirrors, dressing mirrors. Concave Mirror (Converging): Curves inwards like a cave. It can form real, inverted images or virtual, erect, and magnified images, depending on the object's position. *Example:* Shaving mirrors, dentist's mirrors (to get a magnified view of teeth), reflectors in car headlights to produce a strong beam. Convex Mirror (Diverging): Curves outwards. It always forms a virtual, erect, and diminished (smaller) image. Its advantage is providing a wide field of view. *Example:* Car side-view mirrors (with the warning "Objects in mirror are closer than they appear"), security mirrors in shops like Melcom or Shoprite. B. Refraction of Light and Snell's Law
Refraction is the bending of light as it passes from one medium to another (e.g., from air to water). This bending happens because the speed of light changes when it enters a different medium. Refractive Index (n): This is a number that describes how much a medium can bend light. It is the ratio of the speed of light in a vacuum (c) to the speed of light in the medium (v). Formula: `n = c / v` A higher refractive index means the medium is "optically denser" and slows down light more, causing more bending. *Examples:* `n_air ≈ 1.00`, `n_water ≈ 1.33`, `n_glass ≈ 1.50`, `n_diamond ≈ 2.42` Snell's Law: This law mathematically describes how much light bends during refraction. Formula: `n₁ sin(θ₁) = n₂ sin(θ₂)` Where: `n₁` = refractive index of the first medium (where the light is coming from). `θ₁` (theta 1) = angle of incidence (angle in the first medium). `n₂` = refractive index of the second medium (where the light is going to). `θ₂` (theta 2) = angle of refraction (angle in the second medium).