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Investigating Youngs Double Slit Experiment

In the early 1800s, a great issue arose within the medical community, was light a influx or a particle? The famous Isaac Newton, argued that light is at simple fact a particle. On the contrary, a scientist by the name of Thomas Young argued that light was not a particle but that it was a influx. To go along with his debate he devised an test to test his theory. Young performed his famous double slit test which appeared to establish that light was a wave. Though the experiment frequently uses light, the fact is that this sort of experiment can be carried out with any type of influx. Young allowed light from the sun to feed the slit in a barrier so it broadened out in wave fronts from the slit as a source of light. The light then passed through another hurdle with a pair of slits. Each slit diffracted the light as if they were individual but yet identical light resources. The light impacted an observation screen as an disturbance pattern with smart locations and dark areas that spanned out on the screen. The light would only span a certain position before disappearing, that position is ninety diplomas. The brightest part on the display would maintain the center as it could diminish out symmetrically. Light was proven to behave such as a influx with this experiment simply because unlike contaminants waves are able to move through one another, and essentially form disturbance patterns. Needless to say, later on it was established that light experienced both properties of allergens and waves in what would be known as the Wave-Particle Duality. The truth is that both these scientist were correct in their theory. Light can refract, reveal, diffract just like a wave and light can also travel without a medium as being a particle.

Many different facets of the dual slit experiment could have an impact on the results of the experiment. The length the observation display screen is from the foundation of light and the slits affect the results. The wavelength of the light shone through the slits also impacts the results of the test. The distance between your two slits is another factor that affects the results. A method is employed when there is an mysterious variable in a two times slit test:

О» is the wavelength of the light

d is the length between the two slits

x is the length between the rings of light and the central maximum

L is the distance from the slits to the display screen central maximum

The way of measuring of x can only just be dependant on actually experimenting. The wavelength will always be the same because wavelength can only be changed by changing the original light source. The color of the light also depends upon the wavelength. Changing one of the parameters will also change the results as the length being more farther will have a wider diffraction on the observation display.


How can the relationship for dual slit disturbance allow us to anticipate an unknown varying based on known variables?

Purpose: To look for the relationships one of the wavelengths of any source of light and the distances from dark to dark of any double slit interference pattern in order to find the distance between the two double slits.


It is hypothesized that the relationship of double slit interference will allow us to predict unknown variables pretty accurately. Specifically, it is thought that as the wavelengths of the lasers lower, the distances from dark to dark spots on the disturbance style will also decrease by way of a certain factor with regards to the amount of lower. The red laser beam (650 nm) should produce the widest distance between nodal tips on the display screen, while the green laser (532 nm) and crimson laser (405 nm) should produce smaller distances between the nodal factors. Since we stored the distances between your display and the source of light at a constant, it is hypothesized that the wider the wavelengths are, the wider the ranges between your nodal things will be. Furthermore, the distances between the slits are predicted to have about the same width for everyone three of the lasers. Based on the fact that we will be using the same slit for everyone three of the lasers, the determined widths between the slits should be more or less the same. Predicated on our understanding of the formula for destructive interference, we believe that the length between dark to dark will be immediately proportional to the wavelengths of the lasers.

Lab Design:


Meter stick

Two Retort Stands

Two Power Clamps

Twin Slit Plate

Blank little bit of paper

Red Laser (О» = 650 nm)

Green Laser beam (О» = 532 nm)

Purple Laser (О» = 405 nm)

Plastic Ruler

Tissues Paper


1. The required materials were compiled.

2. A bit of blank newspaper was taped contrary to the wall structure, which acted as a display screen.

3. The double slit dish was partially twisted in tissue newspaper and attached to a utility clamp.

4. The power clamp was then attached to the retort stand.

5. The retort stand was positioned far away of 1 meter from the display screen.

6. The red laser beam was placed through to a second tool clamp and the power clamp was clamped onto a second retort stand. Then, it was positioned behind the retort stand keeping the double slit dish.

7. The red laser beam was shined through the double slits and the distances between your dark nodes of the interference pattern on the bare paper was designated with a pencil.

8. The ranges of three successive dark spots were measured using a ruler and registered.

9. Steps 7 and 8 were repeated three times for the red laser beam.

10. Steps 6-9 were repeated, but with the green laser and crimson laser.

11. Every one of the materials were came back to their respective places.

Variable Selection:

Table 1: Usage of the variables

Independent changing:


The lasers were transformed, thus changing the wavelength.

Dependant Variable


The distance between your successive nodes (Оx) improved as the wavelength modified.

Controlled Varying:


The distance from the foundation or slit to the display screen was maintained the same throughout the test.


The D3 slit was used for the entire experiment.


Quantitative Observations:

Table 2: Distance between Bright and Dark Spots for each and every laser


( О» nm )

Оx #1

(± 0. 5mm)

Оx #2 (± 0. 5mm)

Оx #3 (± 0. 5mm)

Red (650)

9. 0

9. 0

10. 0

Green (532)

7. 5

8. 0

8. 0

Purple (405)

4. 5

5. 5


Qualitative Observations:

Red Laser beam: The red laser seemed like a typical everyday laser. The point the laser made was quite little and precise. During the testing, we detected that the red laser beam diffracted the most out all the other lasers. The particular interference style that appeared on the display screen was wider than the interference routine created by the other two lasers.

Green Laser: The inexperienced laser was brighter than the red laser beam. In addition, the idea that the laser made was noticeably bigger than that of the red laser. We also pointed out that the laser appeared to be a little pixelated when shined at the wall structure. The green laser beam pointer itself was noticeably heavier than the red laser. From the real assessment of the laser we observed that the interference pattern made by the green laser was not as huge as that of the red laser beam.

Purple Laser beam: The purple laser was quite fascinating. The point it made on a surface when screening it out was quite noticeably bigger than that of the red and renewable laser. Rather than producing a correct end point like the red laser beam, the purple laser produced a rather large point on the wall membrane. The colour of the purple laser also appeared to go from light to darker as it lengthened from the center of the point. Furthermore, we pointed out that the purple laser was extremely excellent and difficult to look at as it could hurt our eye. During the screening the purple laser beam produced an interference pattern that was not as wide as the prior two lasers.


During our tests we performed 3 tests for each laser to insure that our results were accurate. Obviously, we discovered that our results varied between all three trials for each laser. To find the most accurate representation of, an average of all the tests were be taken.


Table 3: Average of Оx for every Laser

Laser Color

Average Оx ( ± 0. 5mm)


9. 3


7. 8


5. 0

Using these averages we created Graph 1 demonstrating the relationship between your wavelength of the laser and the ensuing value. This graph is very useful because it can be used to assess d (the length between two times slits).

Graph 1: Shows the relation between your wavelength and distance between your successive nodes.

This graph shows the relationship between the change in x and wavelength. It shows that the partnership is linear and this as the x lessens wavelength decreases. The partnership that the graph shows is practical since x and wavelength are regarded as proportional to one another, as one changes the other changes just as. The slope of the lines is -17478x. Since this graph shows the relationship between wavelength and x the slope is in fact also equal to.

Calculating d using Graph 1:

Equation of the slope:

Since the slope is extracted from the graph that presents the relationship:


, L = 1000 mm

± 0. 5mm

ґ the length between the two times slits is

Percent Mistake:

Experimental value = 0. 0572 mm ± 0. 5mm

Actual value = 0. 2636 mm ± 0. 5mm

ґ there can be an problem of 78. 3%.

A percentage mistake of 78. 3% makes sense taking into consideration the amount of mistake present in our experiment. Along the way we should have accumulated a lot of mistake thus adding to the rather high error percentage.

Evaluation of research:

Although, in the beginning we were quite at ease our results it turned out our results were very in appropriate. We followed the procedure step-by-step. We converted our observations effectively. We were able to create a graph to ultimately find d. However, in the long run we were still very in correct. We have everything necessary however we believe that our weakness was that people had several sources of error that got a very large effect on the accuracy in our results. That's our only logical reason for our problem percentage of 78. 3%.

Sources of Problem:

Systematic Problem:

One way to obtain systematic error present in our lab is due to the genuine tool we used to have our measurements. We actually used a very cheap money store ruler to take our measurements. It had been used to gauge the distance between successive nodal lines (О x). The issue with this ruler was that it acquired a lot of tiny potato chips and scrapes onto it which made it difficult to read the measurement on it. In addition, the end of the ruler acquired a bit of it actually chipped off. Overall, it was just in inadequate condition. This source of error experienced a definite effect on the results of your lab. Since it was so difficult to take correct measurements, our measurements of Оx are most likely just a bit inaccurate. This inaccuracy also impacts our calculation because the varying Оx can be an important area of the calculation.

Random Problem:

From the beginning of your laboratory, it was clear that there would be many sources of random mistake. We were doubtful at first of how to proceed and in addition we had to execute the delicate experiment in a rush to meet time constraints. The first of the random problems began when we had to point the laser beam through the slits. The laser itself was create in the right position using a clamp and retort stand. However, when it came to actually pressing the laser beam we ran into issues. The issue was that it was difficult to hold the laser stable while pressing the button at exactly the same time. Often the operator of the laser could not carry it stable for the time period that it took to measure the distances between bright and dark locations. This made it difficult to gauge the distances between dazzling spots since the interference pattern projected on the display was constantly jittering about the screen. Before we could finish measuring the distances effectively the pattern would move and we'd have to remeasure once again. Once again, the fact that it was difficult to accurately assess Оx likely possessed a huge impact of error.

Another random error happened because we were not able to perform the whole experiment within the given time period. We could actually accumulate the results for only two of the lasers in the time given. As a result of this we'd to complete the experiment at a later time. This meant that we had to create the experiment a second time. The potential of mistake was certainly high. In order to eliminate this way to obtain error, we would have to correctly replicate the initial lab setup from a few days before. Obviously, we were not able to replicate the precise conditions of the original lab set up. First of all, we weren't in a position to use the same laboratory bench to set up our experiment. We had to use a lab bench on the far side of the class which might or may not have had a slight difference.

Furthermore, we were tasked with positioning the retort stand the very same distance from the screen as the initial lab set up. We realized we originally positioned the retort stand at a distance of 1 1 m from the display screen. However, it was impossible to know how appropriate our original measurement was and even if we recognized the exact dimension it would be difficult to put the stand at that exact distance. This source of error definitely experienced some sort of effect on our results. The reason being that with respect to the distance from the foundation to the screen the interference style may appear either bigger or smaller on the display screen than the other lasers which were tested under different conditions. Quite simply, the distance between the source and the screen was not held constant even though we were likely to keep it constant. The actual fact that 'L' had not been kept regular definitely added to the inaccuracy of your results.

Improvements to the Lab Procedure:

As shown by the inaccuracy in our results, we definitely possessed a great deal of room for improvement. In all honesty, there were several resources of error within our lab. A good way to improve the laboratory would be actually take additional time to do the lab more carefully. If we had more time we'd have had the opportunity to use our time and be as precise as is feasible in our experiment. We would are also able to finish off the lab in one complete seated so that there was you don't need to re-setup the laboratory again. In all honesty, that one improvement alone would have eliminated a lot of the sources of problem present in our lab. In addition, to boost this lab we're able to find a way to keep carefully the laser completely regular while being pressed. For instance, the button could be taped down so that there would be no need for an operator of the laser which minimizes the shaking involved triggered by unsteady hands.


In summary, Young's two times slit experiment confirmed many unsuspecting things. The hypothesis stated that by interpreting the several areas of the interference routine created by the two times slit allows the prediction of the unidentified factors, d. Although our results weren't as accurate we found that our hypothesis was correct since we were in fact able to find the unidentified changing d using the other known parameters. We also hypothesized that as the wavelength increased or decreased, Оx would do the same. This hypothesis was also right since we detected that as the wavelength of a source decreased, the length between successive nodes also decreased. Furthermore, we found that our hypothesis that the length between two times slits would be equal to be appropriate even though we'd a percent error of 78. 3%. It is evident that systematic and random problem contributed to this somewhat high percent of problem. Although, our laboratory had not been completely successful the experiment taught us several things. From the experiment we learned how the double slit equation applied to true to life, that Оx and wavelength are proportional to one another and most notably, to try to take more attention with our experiments in order to get more accurate results.

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