Summary
When light strikes the borderline between two materials, a part of it reflects and another part refracts
the amount of refraction depends on the indexes of refraction of the two materials and can be calculated by using Snell’s law
for light in a material with larger index of refraction total internal reflection occurs, whenever the angle of incidence exceeds the critical angle.
Lenses are glass pieces with curved surfaces, that are used to converge or diverge parallel light rays through refractions
Lenses are characterized by their focal lengths, or dioptries
Lenses can be converging or diverging
The images of objects produced by lenses can be determined constructing some special light rays
Lenses can produce real and virtual, magnified or reduced size images
Ideal lenses are very hard to produce: lenses have aberrations
Application of lenses: cameras, eyeglasses, magnifying glass, microscope, telescope