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: 1st Term
Week: 17
Grade code: 1.2.2.LI.3
Strand code: 2
Sub-strand code: 2
Content standard code: 1.2.2.CS.2
Indicator code: 1.2.2.LI.3
Theme: ENERGY
Subtheme: WAVES
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This lesson moves us from drawing ray diagrams to a more precise, mathematical way of understanding how mirrors work. We see mirrors everywhere in Ghana – from the side mirrors on a tro-tro or an Okada, to the security mirrors in Melcom, to the makeup mirrors used at home. Today, we will learn the formulas that engineers and scientists use to predict exactly where an image will form, how large it will be, and what its nature is. By mastering the Mirror Formula and Magnification Formula, you will be able to solve problems related to any spherical mirror accurately.
A. Recap of Key Terms
Before we use the formulas, let's remember our terms with a diagram. Object distance (u): The distance from the pole (P) of the mirror to the object. Image distance (v): The distance from the pole (P) of the mirror to the image. Focal length (f): The distance from the pole (P) to the principal focus (F). Remember, f = R/2, where R is the radius of curvature. Object height (h_o): The height of the original object. Image height (h_i): The height of the formed image. B. The "Real is Positive" Sign Convention
This is the most important rule for using the formulas correctly. It helps us translate a physical situation into mathematics. Think of the mirror as a dividing line.
| Quantity | When is it POSITIVE (+)? | When is it NEGATIVE (-)? | | :--- | :--- | :--- | | Object distance (u) | Always for a single mirror system (real object). | (Not relevant for SHS1) | | Image distance (v) | Image is REAL (formed in front of the mirror, can be caught on a screen). | Image is VIRTUAL (formed behind the mirror, cannot be caught on a screen). | | Focal length (f) | For a CONCAVE mirror (converging mirror). | For a CONVEX mirror (diverging mirror). | | Magnification (m) | Image is UPRIGHT / Erect (virtual). | Image is INVERTED (real). | | Image Height (h_i) | Image is UPRIGHT / Erect. | Image is INVERTED. |