Credit: Petr Kratochvil
License: CC BY-NC 3.0
Light refracted through water.
Optics is the study of light. Geometric optics is the classical science of mirrors, glass, and lenses. It explains how light bends in water, and how images are formed in mirrors, telescopes, microscopes, and other devices.
1. The law of reflection states that the angle of incidence is equal to the angle of reflection
The incident ray, the reflected ray and the normal are also coplanar.
2. For the object distance, the image distance , and the focal length , both the mirror equation and thin lens equation is
3. For spherical mirrors,
4. The lateral magnification of an object is defined as the ratio of the image height of the object to the actual height of the object, and is equal to the negative of the ratio of the image distance to the object distance
5. We define the ratio of the speed of light through vacuum to the speed of the light through a particular medium as the index of refraction
Since , the index of refraction is always greater than 1 when traveling through any medium other than vacuum.
6. Snell’s law can be defined in terms of the indices of refraction or the speeds of light in the two media. It expresses the relationship between the angle of incidence and the angle of refraction at the interface of two media.
The index of refraction is the medium from which light originates and is the index of refraction of the medium to which light passes. Angle is measured with respect to the normal at the interface of medium 1 and angle is measured with respect to the (same) normal at the interface of medium 2. Snell’s law can be expressed in terms of the velocities of light in the respective media as
where is the speed of the light in medium 1 and is the speed of light in medium 2.