Short Summary

Chapter 10, Light – Reflection and Refraction, details the behaviour of light rays when they reflect from spherical surfaces and refract through different transparent media. Reflection follows the law that the angle of incidence is equal to the angle of reflection. Concave mirrors converge light and can form real or virtual images, whereas convex mirrors diverge light and consistently form virtual, erect, and diminished images. The mirror formula relates focal length, object distance, and image distance as 1/f = 1/v + 1/u. Refraction occurs when light changes direction while passing obliquely between media of different optical densities because its speed changes. According to Snell’s Law, the ratio of sin i to sin r remains constant for a given pair of media, and the absolute refractive index of a medium is given by n = c/v, where c is the speed of light in vacuum and v is the speed of light in the medium. Lenses use refraction to focus light, with convex lenses converging rays and concave lenses diverging them. The positions and sizes of images formed by lenses can be determined using the lens formula, 1/f = 1/v − 1/u. The power of a lens represents its ability to converge or diverge light and is calculated as P = 1/f, where the focal length is measured in metres, and the power is expressed in dioptres (D).