Optics
Unit 6. Covers Reflection by spherical mirrors; Refraction and total internal reflection; Lenses; Prism; Optical instruments; Wave optics.
About this unit
Optics studies light. The first part is ray optics, which treats light as rays travelling in straight lines: reflection by spherical mirrors, refraction at plane and curved surfaces, total internal reflection, thin lenses, refraction and dispersion through a prism, and optical instruments such as the microscope and telescope. All of these rest on two laws (reflection and refraction) and a consistent sign convention. The second part is wave optics, which explains effects that rays cannot: Huygens' principle, interference of light in Young's double-slit experiment, and diffraction at a single slit. Together they explain how images are formed and why light shows wave behaviour.
How to prepare
Fix the Cartesian sign convention first and use it every time. Memorise the mirror formula, lens formula, lens maker's formula, refraction at a spherical surface, prism formula, magnification of instruments, fringe width and single-slit minima. Solve many numericals with careful signs and units. Learn image-formation cases for mirrors and lenses and the conditions for total internal reflection and sustained interference.
Topics in this chapter
Reflection by spherical mirrors
Mirror formula.
5 questionsRefraction and total internal reflection
Refraction at spherical surfaces and optical fibres.
5 questionsLenses
Thin lens and lens maker’s formulae, magnification, power and combinations.
6 questionsPrism
Refraction and dispersion through a prism.
5 questionsOptical instruments
Microscope and astronomical telescope.
5 questionsWave optics
Huygens’ principle, interference, Young’s double-slit experiment and single-slit diffraction.
5 questions