Description: After studying this lesson, you should be able to learn about, reflection at curved surfaces and establish the relationship between the focal length and radius of curvature of spherical mirrors, sign convention for spherical surfaces, the relation between the object distance, the image distance and the focal length of a mirror as well as a spherical refractive surface, the laws of refraction, total internal reflection and its applications in everyday life, Newton's formula for measuring the focal length of a lens, displacement method to find the focal length of a lens, an expression for the focal length of a combination of lenses in contact