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: 13
Grade code: 1.2.2.LI.3
Strand code: 2
Sub-strand code: 2
Content standard code: 1.2.2.CS.1
Indicator code: 1.2.2.LI.3
Theme: ENERGY
Subtheme: WAVES
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This lesson explores the fascinating phenomenon of multiple images formed when two plane mirrors are placed at an angle to each other. We will investigate how light waves, upon reflection, can create a multitude of images from a single object. This principle is not just a concept in a physics textbook; it's visible in our everyday lives, from the way a barber uses two mirrors to show you the back of your head, to the beautiful, symmetrical patterns you see in a kaleidoscope. By understanding this, we learn more about the predictable behaviour of light and how we can manipulate it for practical and artistic purposes.
A. Recap: Reflection in a Single Plane Mirror
Before we look at two mirrors, let's remember what happens with one. A single plane mirror forms one image of an object. This image is: Virtual: It cannot be formed on a screen. Upright (Erect): It is the same way up as the object. Laterally Inverted: The left side appears as the right side (like when you read text in a mirror). Same size as the object. Located as far behind the mirror as the object is in front of it.
This happens because light waves from the object strike the mirror and reflect according to the Laws of Reflection: The incident ray, the reflected ray, and the normal at the point of incidence all lie in the same plane. The angle of incidence (i) is equal to the angle of reflection (r). B. Multiple Reflections in Inclined Mirrors
When we place two mirrors at an angle to each other, something amazing happens. Light from an object can reflect off the first mirror, then the reflected ray can travel to the second mirror and reflect again. The image formed by the first mirror acts as a virtual object for the second mirror, which then forms a new image. This process can continue, with images of images being formed, creating a pattern of multiple images.