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: 12
Grade code: 1.2.2.LI.2
Strand code: 2
Sub-strand code: 2
Content standard code: 1.2.2.CS.1
Indicator code: 1.2.2.LI.2
Theme: ENERGY
Subtheme: WAVES
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This lesson introduces the fundamental principles of how light behaves when it encounters a smooth, shiny surface like a mirror—a phenomenon called reflection. We see our world because of reflection. From looking at ourselves in a mirror before school, to seeing the moon shine at night (it reflects the sun's light), to the way a car's side mirror helps a driver navigate the busy streets of Accra or Kumasi, reflection is all around us. By understanding the simple but powerful laws that govern reflection, we can understand how mirrors work and why we see images in them. This lesson will be a hands-on, experiential journey to discover these laws for ourselves.
2.1 What is Reflection? Reflection is the bouncing back of a wave, such as light, when it hits a boundary or surface that it cannot pass through.
Imagine throwing a tennis ball against a smooth wall. It bounces off. Light behaves in a similar way. When light from a source (like the sun or a light bulb) hits an object (like a mirror or this page), it bounces off. Our eyes detect this bounced light, which is how we see the object.
There are two main types of reflection: Regular (or Specular) Reflection: This happens when light hits a very smooth, polished surface like a plane mirror, the surface of calm water in the Volta Lake, or a shiny metal spoon. All parallel incident rays are reflected in the same direction, which allows a clear image to be formed. Irregular (or Diffuse) Reflection: This happens when light hits a rough surface, like a wall, a piece of paper, or a wooden desk. The surface might look smooth to us, but at the microscopic level, it is rough. Parallel incident rays are scattered in many different directions. This is why you can see the wall, but you can't see your reflection in it. 2.2 Terminology of Reflection To understand the laws of reflection, we must first understand the language used to describe it. Let's use a diagram to explain.
*Imagine a flat, horizontal line representing a plane mirror. A ray of light comes from the top left and strikes the mirror at a point. It then bounces off towards the top right.*