Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Define and explain the laws of reflection and refraction.
• Apply Snell's Law to solve for angles and refractive indices.
• Explain total internal reflection and its applications.
• Solve problems involving reflection and refraction.
• Describe the relationship between refractive index, speed, and wavelength.

Lesson summary

Geometrical optics is a branch of optics that deals with light as rays travelling in straight lines. This approximation is valid when the wavelengths of light are much smaller than the objects with which the light interacts. This week, we will explore the fundamental principles governing how light interacts with different surfaces, specifically focusing on reflection and refraction. Understanding these principles is crucial in many aspects of South African life, from the design of solar panels that power our homes to understanding how corrective lenses in eyeglasses improve our vision, and even how security cameras work to keep our communities safe.

Lesson notes

2. 1.

Nature of Light: Ray Model Geometrical optics simplifies the behavior of light by treating it as rays that travel in straight lines. While light also exhibits wave-like properties, the ray model is sufficient for understanding many optical phenomena, particularly when dealing with objects much larger than the wavelength of light. 2.

2. Reflection Reflection occurs when light bounces off a surface.

There are two main types of reflection: Specular Reflection: Reflection from a smooth surface (like a mirror), where the reflected rays are parallel, producing a clear image.

Diffuse Reflection: Reflection from a rough surface, where the reflected rays scatter in many directions.

Laws of Reflection: The incident ray, the reflected ray, and the normal (a line perpendicular to the surface at the point of incidence) all lie in the same plane. The angle of incidence (θ i ) is equal to the angle of reflection (θ r ). θ i = θ r