Young’s double-slit experiment

The behaviour of light, as a rule, depicts the conduct of apparent, bright, and infrared light. The experiment is demonstrated by Young’s double-slit experiment, or the modern, two-slit experiment, or the double-slit experiment, that both light and matter exhibit properties of both wave and particle. Apart from this, the experiment also shows the probabilistic nature of quantum mechanical phenomena. Young’s double-slit experiment was originally performed by Thomas Young in 1801.

Many scientific theories fail in front of this experiment, and it has also shaken Quantum Mechanics. Let us know how Young’s Double Slit Experiment challenged the existence of modern science.

In this experiment, two parallel thin slits were made on a metal plate. This slit had a light source on one side and a curtain or board on the other. Patterns are formed on the screen by the passage of light through the slits. The laws of light are studied by analysing these patterns. This experiment was first done by the 18th-century scientist Thomas Young. Hence, this experiment is called Thomas Young’s Double Slit Experiment.

Let’s take the point of the ‘light source’: a circular wavefront is being emitted from it. A rectangular cardboard M is placed at a distance b from a point type source S.

Two holes, S1 and S2, are made at the same distance from the point O of the cardboard; the distance between them is d. The curtain is kept at a distance D from the rectangular cardboard M. When a point (light) is incident from a source (S) on S1 and S2, then S1 and S2 behave like a two-phase relationship of light sources, from which the light is transmitted forward in the form of secondary waveforms. These secondary wavelets are transmitted between the rectangular cardboard M and the screen N, and after transmission, these secondary wavelets are superimposed on the screen, resulting in an interference pattern.

At the points where the crests of light waves meet, compensatory interference occurs, and bright or bright fringes are obtained on the screen and at the points at which the trough of light waves meet. That is, at those points, ‘destructive interference’ takes place, and a black fringe is obtained on the screen.

In Young’s double-slit experiment, bright and dark fringes are obtained in an alternate sequence on the interference pattern screen.

The distance between two consecutive bright fringes or two consecutive non-luminous fringes is the same.

Fringe Width (): The distance between two consecutive bright fringes or two consecutive non-luminous fringes is called fringe width. It is denoted by (beta). Its unit is metre (m).

Let the distance between the two holes A and B be d and the distance between the screen from these points is D as shown in the figure and be the wavelength λ of the light emerging from the holes.

A light wave travelling from points A and B meets the screen P here they can be in the same phase and also in the opposite phase, depending on the distance travelled by them, the distance of this point P from the central fringe is x.

So the path difference between the interference waves δ = xd/D

Here thetais considered small.

Position of bright fringe

According to the principle of interference, the condition for path difference of a complementary interference = nλ

 xd/D = nλ

Here n = 1,2,3, ……… This is the order of the bright fringe.

 Thus, for nth bright fringe, x = (D/d) nλ

Position of the dark fringe 

According to the law of interference, the path difference of a malnourished wave interference = (2n-1)λ/2

Here n = 1,2,3, ……… This is the order of the dark fringes.

Thus, the case for nth dark fringe x = (D/d) [(2n – 1)λ/2]

Width of fringe

The distance between two consecutive bright and non-luminous fringes is called the width of the fringe.

Fringe width β = Dλ/d

Constructive and Destructive Interference

For constructional interference, the method difference must be a significant frequency of the wavelength. 

So for a bright fringe to be at ‘y’,

nλ = y d/D

Or, y = nλD/d

Where n = ±0,1,2,3…..

The 0th fringe represents the bright middle fringe.

Similarly, the expression of the black fringe in the Young double-slit test can be obtained by setting the method difference by:

Δl = (2n+1)λ/2

This simplifies to

(2n+1)λ/2 = y d/D

y = (2n+1)λD/2d

Young’s double-slit experiment was a watershed moment in scientific history because it ensured that light behaved like a wave.

The Double Slit Experiment was later made using electrons, and to everyone’s surprise, the pattern formed was exactly as expected in light. This can permanently change our understanding of matter and particles, forcing us to accept that things like light also behave like waves.

Some results came out in it which were as follows –

1. Some bright bands are found on the curtain which is kept, which are called bright fringes, and some black strips are found, which are called dark fringes. Furthermore, these bright and dark fringes are obtained in alternate order. When bright fringes and dark fringes are obtained in an alternate sequence, then the group of these fringes is called an interference pattern.
2. The intensity of all the bright stripes, i.e. the bright fringes obtained on the screen, and the intensity of all the black strips — the dark f, ranges remain the same. Out of which, the intensity of the bright fringes is maximum, and the intensity of the dark fringes is minimum or almost zero.
3. Simultaneously, it was also seen that the distance between any two bright or bright fringes received on the screen or any two black or dark fringes remains the same, and the distance is also called the width of the fringe.
4. All bright and dark fringes have the same width.

Thus, these were some of the results obtained based on Young’s double-slit experiment.

Conclusion

The mystery of not understanding light raises many big questions about science. For example, are the basic principles of our science wrong? Is there some supreme being who wants to keep its hidden secrets hidden? Is every particle controlled by some supreme being? Perhaps in the future, the reason for this may be known exactly, but at the moment, it will not be wrong to understand the result of the Double Slit Experiment, the proof of the existence of God.