The key difference between total internal reflection and refraction is that total internal reflection is the complete underwater appearance with no loss of brightness, whereas refraction is the change in the direction of a wave that is passing from one medium to another.
Total internal reflection and refraction are optical phenomena that are discussed mainly under physics and analytical chemistry.
CONTENTS
1. Overview and Key Difference
2. What is Total Internal Reflection
3. What is Refraction
4. Total Internal Reflection vs Refraction in Tabular Form
5. Summary – Total Internal Reflection vs Refraction
What is Total Internal Reflection?
Total internal reflection or TIR is an optical phenomenon that describes the underwater light reflection, which appears as a mirror with no loss of brightness. Generally, this type of reflection occurs when the waves in a medium strike sufficiently against the boundary with another medium, which occurs externally. There, the waves tend to travel faster in the second medium than the first one, and the second medium should be perfectly transparent to the waves. Typically, total internal reflection occurs with electromagnetic waves such as light and microwaves, but also it can occur with some other waves such as sound and water waves.
We can describe the total internal reflection of light using a semicircular cylindrical block of common glass or acrylic glass. There, a “ray box” projects a narrow beam of light radially inward. Then the semicircular cross-section of the glass allows this narrow beam of light to remain perpendicular to the curved portion of the air/glass surface, thereby continuing in a straight line towards the flat area of the surface, but the angle of light with the flat area varies.
Figure 01: Total Internal Reflection in an Aquarium
Let us now look at some everyday examples for total internal reflection. When we stand beside an aquarium, having our eyes below the water level, we can see fish and submerged objects reflected in the water and air surface. Here, the brightness of the reflected image is usually startling. Similarly, when we open our eyes while swimming just below the water surface, the surface appears like a mirror reflecting objects below if the water is calm.
What is Refraction?
Refraction is the change in the direction of a wave that is passing from one medium to another. This also occurs if there is a gradual change in the same medium. Light is the most common subject in the refraction phenomenon, but there are some other waves involved as well, including sound waves and water waves. We can determine the amount of refraction of a wave by observing the change in wave speed and the initial direction of the wave propagation in relation to the direction of the change in the speed.
Figure 02: Refraction Follows Snell’s Law
In the case of light, the refraction follows Snell’s law. This law states that for a given pair of media, the ratio between the sin value of the angle of incidence and the angle of refraction is equal to the ratio between the phase velocities in those two media, and equivalently, it is equal to the ratio of indices of refraction of the two media.
Typically, the optical prisms and lenses tend to use refraction of light in order to redirect light, which also occurs in the human eye. There, the refractive index of the materials tends to vary with the wavelength of light; therefore, the angle of the refraction varies as well. We call it ‘dispersion”, and it causes prisms and rainbows to divide the white light into its constituent spectral colors.
What is the Difference Between Total Internal Reflection and Refraction?
Total internal reflection and refraction are optical phenomena that are discussed mainly under physics and analytical chemistry. The key difference between total internal reflection and refraction is that total internal reflection is the complete underwater appearance with no loss of brightness, whereas refraction is the change in the direction of a wave that is passing from one medium to another.
The following infographic summarizes the difference between total internal reflection and refraction in tabular form.
Summary – Total Internal Reflection vs Refraction
Total internal reflection and refraction are two optical phenomena. The key difference between total internal reflection and refraction is that total internal reflection is the complete underwater appearance with no loss of brightness, whereas refraction is the change in the direction of a wave that is passing from one medium to another.
Reference:
1. “Refraction – Definition, Laws, Solved Problems, Applications.” BYJUS, BYJU’S, 31 Mar. 2021.
Image Courtesy:
1. “Nautilis Reflected Above (17567356012)” By Eric Kilby from Somerville, MA, USA – Nautilis Reflected Above (CC BY-SA 2.0) via Commons Wikimedia
2. “Snells law” By Cristan at English Wikipedia, Sawims at Dutch Wikipedia – This file was derived from Wet van snellius.svg (Public Domain) via Commons Wikimedia