Ray Optics and Optical Instruments
A comprehensive study of light behaviour using the ray model, covering reflection by spherical mirrors, refraction at plane and curved surfaces, total internal reflection, lenses, prisms, dispersion, and optical instruments including the human eye, microscopes, and telescopes
Topics
Introduction to Ray Optics and Reflection by Spherical Mirrors
What light is, why the ray model works, the speed of light in vacuum, rays and beams, the laws of reflection, and the key terms used to describe spherical mirrors
Sign Convention and Focal Length of Spherical Mirrors
The Cartesian sign convention for measuring distances in optics, and the meaning, location, and derivation of the focal length of spherical mirrors
The Mirror Equation and Magnification
Deriving the mirror equation relating object distance, image distance, and focal length, along with the magnification formula and their application to concave and convex mirrors
Refraction of Light
How light changes direction when it passes from one transparent medium to another, Snell's law, refractive index, lateral shift through a glass slab, and apparent depth
Total Internal Reflection
How light travelling from a denser medium to a rarer medium can get completely trapped inside, the critical angle, its formula, and a simple laser demonstration
Applications of Total Internal Reflection
How total internal reflection is used in reflecting prisms to bend and invert light, and in optical fibres to transmit signals over long distances with almost no loss
Refraction at Spherical Surfaces
How light bends when it crosses a curved boundary between two media, the derivation of the refraction formula relating object distance, image distance, refractive indices, and radius of curvature, and a worked numerical example
Refraction by Lenses: The Lens Maker's Formula and Thin Lens Equation
How a lens forms images by refracting light at two spherical surfaces, the step-by-step derivation of the lens maker's formula and thin lens equation, ray diagram rules for convex and concave lenses, magnification, and a worked example on making a lens optically invisible
Power of a Lens
How the power of a lens quantifies its bending ability, the dioptre as its unit, the sign convention for converging and diverging lenses, and fully worked problems on computing power, finding refractive index from curvatures, and comparing focal lengths in air versus water
Combination of Thin Lenses in Contact
How placing two or more thin lenses in contact produces an equivalent single lens, the derivation of the combined focal length formula, power addition, magnification as a product, and a fully worked three-lens numerical problem
Refraction through a Prism
How light bends through a triangular prism, the geometry linking angle of incidence, emergence, and prism angle to deviation, the minimum deviation condition, the prism formula for refractive index, and the thin prism approximation
Optical Instruments: The Microscope
How a simple magnifying glass and a compound microscope work, the derivation of magnification for both near-point and relaxed-eye viewing, the role of the objective and eyepiece in a compound microscope, and a fully worked numerical example
Optical Instruments: The Telescope
How refracting and reflecting telescopes work, the magnification formula for an astronomical telescope, why large-diameter objectives matter for light gathering and resolving power, the Cassegrain reflector design, and notable telescopes around the world