Lesson Notes By Weeks and Term v4 - SHS 3
WAVE
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
WAVE
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Physics
Class: SHS 3
Term: 2nd Term
Week: 1
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
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
This lesson explores the fascinating world of lasers. While we often see lasers in movies or as simple pointer tools, the physics behind them is a powerful application of our understanding of atoms and light waves. In Ghana, lasers are not just science fiction; they are crucial for the technology that powers our internet (fibre optics), modern medical procedures in hospitals like Korle-Bu, and large-scale construction projects across the country. By understanding how a laser beam is produced, we gain insight into one of the most important inventions of the 20th century and its impact on our daily lives.
A. What is a LASER?
The word LASER is an acronym that describes exactly what it does: Light Amplification by Stimulated Emission of Radiation
Let's break this down. A laser is a device that creates and amplifies a special kind of light through a process called stimulated emission. "Radiation" here simply refers to electromagnetic radiation, which includes light. B. The Physics Behind the Light: Atomic Energy Levels
To understand how a laser works, we must first remember how atoms interact with light. Energy Levels: Electrons in an atom can only exist in specific energy levels or "shells". The lowest, most stable energy level is called the ground state. Higher energy levels are called excited states. Absorption: An atom can jump from the ground state to an excited state by absorbing a packet of light energy, called a photon. For this to happen, the incoming photon must have the *exact* amount of energy corresponding to the difference between the two energy levels (`ΔE = E₂ - E₁`). Emission: An atom in an excited state is unstable and will eventually fall back to a lower energy level. When it does, it releases the excess energy as a photon of light. There are two ways this can happen. C. Spontaneous Emission vs. Stimulated Emission