What is the difference between refraction and refractive index

When n 1 is greater than n 2 , the angle of refraction is always larger than the angle of incidence. Alternatively when n 2 is greater than n 1 the angle of refraction is always smaller than the angle of incidence. In optical microscopy, refractive index is an important variable in calculating numerical aperture, which is a measure of the light-gathering and resolving power of an objective.

In most instances, the imaging medium for microscopy is air, but high-magnification objectives often employ oil or a similar liquid between the objective front lens and the specimen to improve resolution. The numerical aperture equation is given by :. Snell's law was originally defined by the relationship between the incident angles and the ratio of the velocities of light in the two media.

As the refractive index of a material increases, the greater the extent to which a light beam is deflected or refracted upon entering or leaving the material.

The refractive index of a medium is dependent to some extent upon the frequency of light passing through, with the highest frequencies having the highest values of n. 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 all in one plane. Mirrors work by reflecting light that fall on it. In comparison, transparent glass reflects little of the incident light and lets most of it pass through. Refraction is a phenomenon that happens when a wave goes from one medium into another.

Here, the ray bends as it passes from one medium to the other. Absolute refractive index of a medium is a number that describes how much a ray of light would bend if the ray came from a vacuum and entered that medium. How the ray bends depends on the absolute refractive indices of the two media. If the ray goes from a medium with a lower absolute refractive index into a medium with a larger absolute refractive index, then the ray bends towards the normal.

If the second medium has a lower refractive index than the first, then the ray bends away from the normal. In the above diagram, and refer to the absolute refractive indices of air and water respectively, and in this case , and so the ray bends towards the normal. Figure Medium Light returns to the same medium. Light travels from one medium to another.

Waves Bounce off the plane and changes direction. Pass through the surface, that changes their speed and direction. Angle of incidence Equal to the angle of reflection. Not equal to the angle of refraction. Occurence Mirrors Lenses. In simple terms, reflection implies the rebounding of light, sound, heat or another object back to the source, without absorbing it.

It alters the direction of the beam of light, when it falls on the plane, amidst two media, so that the ray goes back to the medium, in which it is generated. The law of reflection says:. These two principles are apposite to all kinds of reflecting planes. Reflection can be of two types:. Refraction can be understood as the phenomenon of light, wherein the wave is diverted when it passes diagonally through the interface between two media of different densities.

It refers to the shift in direction and speed of the beam of light or radio waves, because of the change in transmission medium.