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: 19
Grade code: 3.2.2.LI.1
Strand code: 2
Sub-strand code: 2
Content standard code: 3.2.2.CS.2
Indicator code: 3.2.2.LI.1
Theme: ENERGY
Subtheme: WAVE
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Today, we are exploring a special kind of light that is all around us but very different from the light from the sun or a light bulb. This light is called a LASER. We see it used in barcode scanners at Melcom or Shoprite, in construction for measuring straight lines, in hospitals for surgery, and in the fibre optic cables that bring internet to our phones and homes from providers like MTN and Vodafone. Understanding how a laser works helps us appreciate the amazing technology we use every day. We will learn the fundamental physics principles that make this powerful and precise light possible.
What is a LASER? LASER is an acronym that stands for Light Amplification by Stimulated Emission of Radiation.
Unlike ordinary light (e.g., from a fluorescent tube), laser light has four unique properties: Monochromatic: It consists of a single colour or wavelength. For example, a red laser pointer produces only red light of a very specific wavelength. Coherent: All the light waves are in phase. This means the crests and troughs of all the waves line up perfectly, making the wave very organised and powerful. Think of soldiers marching in perfect step versus a crowd of people walking randomly. Directional: The beam is very narrow and does not spread out much over long distances. A torchlight beam spreads out quickly, but a laser beam can travel kilometres and remain a small dot. High Intensity: Because the energy is concentrated in a narrow beam, laser light is extremely intense and powerful. The Core Principles of Laser Production
To understand how a laser works, we must look at the behaviour of electrons inside atoms.
A. Energy Levels and Photon Interaction Electrons in an atom exist in specific energy levels or shells. The lowest energy level is called the ground state. Higher energy levels are called excited states. An electron can jump to a higher energy level by absorbing energy, usually from a photon of light. This is called absorption. An electron in an excited state is unstable and will eventually fall back to a lower energy level, releasing the extra energy as a photon of light. This is called emission.