Lesson Notes By Weeks and Term v4 - SHS 3
WAVE
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WAVE
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Subject: Physics
Class: SHS 3
Term: 1st Term
Week: 20
Grade code: 3.2.2.LI.3
Strand code: 2
Sub-strand code: 2
Content standard code: 3.2.2.CS.1
Indicator code: 3.2.2.LI.3
Theme: ENERGY
Subtheme: WAVE
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Welcome, future scientists and engineers! Today, we are exploring one of the most important tools in the world of optics: lenses. Lenses are not just pieces of curved glass; they are the heart of many devices we use every day in Ghana. From the spectacles that help our grandparents read the Bible or the Daily Graphic, to the camera on your phone that captures memories at Independence Square, to the projectors used in our churches and schools, lenses are everywhere. Understanding how lenses form images using mathematics allows us to design and build these amazing tools.
This section contains the core knowledge you need. Pay close attention to the formulas and especially the sign conventions, as they are the key to success. A. The Thin Lens Formula
The relationship between the object distance, the image distance, and the focal length of a thin lens is given by a simple but powerful equation known as the Lens Formula or Lens Equation.
> Formula: > > $$ \frac{1}{f} = \frac{1}{u} + \frac{1}{v} $$ > > Where: > * `f` = focal length of the lens. This is the distance from the optical centre to the principal focus. > * `u` = object distance. This is the distance of the object from the optical centre of the lens. > * `v` = image distance. This is the distance of the image from the optical centre of the lens. > > *All distances are measured in the same unit, usually metres (m) or centimetres (cm).* B. The "Real is Positive" Sign Convention
To use the lens formula correctly, we must follow a set of rules for signs. The most common convention used in WASSCE is the "Real is Positive" convention. It is simple and logical.