Ray Optics-Refractive Index

The reflective index is also known as the index of refraction, it is supposed to measure the bending of a ray of light when it passes from one side to another. If i is the angle of the given incidence in the ray of a vacuum (and the angle that is between the present incoming ray and the given perpendicular of the surface of the given medium called as the normal). 

Moreover, r is the given angle of refraction and it is also the (angle in between the given ray in the particular medium and the normal), the given refractive index n can also be defined as the particular ration of the sine of the given angle of the incidence to the particular sine of the angle of refraction such as; n = sin i / sin r. Refraction of index is also known to be equal to the velocity of light c and a given wavelength inside an empty area which is divided by the given velocity in a particular substance, or n = c/v.

Formula for the refractive index

The formula for index of refraction is n = c / v.

The index of refraction is n.

In a vacuum, c is the speed of light (or air)

In the media, v is the speed of light (e.g. water, olive oil, etc.)

Snell’s Law

The refraction and incidence angles are related to the refraction indices of the relevant medium by Snell’s Law. According to Snell’s Law, the product of the sine of the angle created by the light beam, the normal straight line, and the media’s refractive index must be constant.

The Refraction Laws

There are two laws of refraction that govern the behaviour of light at the site of refraction, and what we see is the refracted picture generated by the object.

The refracted ray, incident or obliquely falling ray, and normal beam will all tend to lay together in the same plane at the point of incidence.

Second, according to Snell’s law, the ratio of sin of the angle of incidence to refraction is constant or has a fixed value.

n1sin(i) = n2sin(r)

The refractive indices of the two mediums involved define i = angle of incidence and r = angle of refraction, which are fixed quantities. It is proportional to them and has no dimensions.

The refractive index fluctuates depending on the wavelength.

A material’s refractive indices change with wavelength. In many materials, the refractive index varies by a few percentage points for each wavelength. The most common way to report a refractive index is to use a single n value, such as 633 nm.

Refraction

When light passes from one medium and into another, it changes direction and is refracted. When white light is refracted, it splits into hues, producing this effect. Prims and rainbows have the same effect. The angle of refraction is less than the angle of incidence when light passes through a substance having a higher refractive index. As a result, light is refracted in the direction of the surface’s normal. When light passes through a material having a lower refractive Index, it refracts away from the normal, moving closer to the surface.

The Absolute Refractive Index 

(ARI) is a measurement of how well a lens reflects light. The ratio of the speed or velocity of light in a vacuum (c) to the speed or velocity of light in the material medium (v) on which it falls is the refractive index of a material medium. The refractive index or index of refraction for a media is determined by the formula: Small n signifies or denotes the refractive index or index of refraction for a medium, which is determined by the formula:

           nv = c/v

Where c denotes the speed or velocity of light in vacuum, and v denotes the speed or velocity of light in the medium supplied.

Applications

• Provides an idea of the absolute refractive index of a range of materials other than vacuum and air that we may use in the lab.
• Is used in the production of particular compounds with well-defined refractive indices.
• In the pharmaceutical sector, they’re used to gain a rough notion of a chemical’s optical density.
• Absolute refractive index values are commonly used to identify optically denser from optically uncommon materials.

The Relative Refractive Index (RRI) 

The refractive index of one material medium in comparison to another is referred to as the relative refractive index. Where the initial medium is not vacuum, the relative refractive index may be calculated using the following velocities of light in different media:

          n21 = v1/v2

The refractive index of the speed of light in medium 2 in comparison to the speed or velocity of light in medium 1 is n21.

In the same way, we may compute the refractive index of 1 in relation to 2. The velocity of light in medium 2 as a percentage of the velocity of light in medium 1.

        n12 = v2/v1

A light beam bends towards normal when it travels from a rarer to a denser medium, and it bends away from normal when it travels from denser to rarer. Because ice has a lower refractive index than kerosene, the light beam bends towards the normal as it travels from ice to kerosene, and their ratio may be used to compute the relative refractive index.

Applications

• It is frequently utilised or employed for identifying a material, validating its purity, or detecting the concentration of a chemical.
• It’s commonly used to figure out how much of a solute is in an aqueous solution. The sugar content may be determined using the refractive index of a sugar solution, for example.
• It may also be used to determine drug concentrations in the pharmaceutical and pharmacy businesses.
• It’s often used to calculate prism dispersive power and the focusing power of various lenses.
• It’s also used to calculate the thermophysical properties of various hydrocarbons and petroleum mixtures.

Conclusion

The idea of refractive index extends across the electromagnetic spectrum, from X-rays to radio waves. It can also be used to describe wave phenomena like sound. In this situation, the speed of sound is employed rather than the speed of light, and a reference medium other than vacuum must be used. A lens made of a high refractive index material is thinner and thus lighter than a lens made of a lower refractive index material for lenses (such as eyeglasses). The cost of producing such lenses is typically higher than that of conventional lenses.