Double slit experiment

The Infamous Double Slit Experiment

Kirtan Purohit 40764145

• The double slit experiment was one of the most famous experiments in quantum mechanics. Carried out by Thomas Young in the 1800’s it revolutionized physics.

• The basis for Young’s experiment was firing electrons through 1 slit then 2 slits and observing the resulting pattern on the wall behind the slits. We can first consider what would happen with paintballs and water waves in such an experiment.

• If one fires paintballs through appropriate slits, the wall behind the paintballs will appear to have 2 steady lines of paintball splashes, as such. Thus the paintballs can be said to behave as particles

Source: http://2.bp.blogspot.com/-H5EP1hTIqTY/TmzYrE9C5iI/AAAAAAAAALo/43A1LBKLUaI/s1600/youngexp2.gif

paintballs

• If one were to repeat the experiment, but with waves hitting the slit instead the following could be observed.

• The top of one wave and the bottom of an another would hit each other and cancel each other out. We have learned about this already in physics in our waves unit. This would result in a diffraction pattern where the middle would have the highest intensity.

http://www.projectalbatross.com/wp-content/uploads/2013/03/waves.png

Young attempted this ‘double-slit’ experiment at first with one slit. Since electrons are like tiny balls of matter they lined up perfectly behind the slit on the wall. Thus helping the hypothesis of behaving as particles.

Then he attempted the experiment with two slits. Something marvelous was observed.

The electrons went through the two slits and a interference pattern of many bands was observed. Thus one could conclude reasonably that electrons behave as waves, although surprising it could

have been possible. However the experiment was taken further by . . .

http://upload.wikimedia.org/wikipedia/commons/5/57/Double-slit.PNG

Observing what the electron does as it goes through the two slits. A measurement device was set up to see how the electrons went through the slits. The result was

extraordinary. Electrons began behaving as particles again. That is to say they lined up perfectly behind the two slits instead of an interference pattern. This was incredible! The simple act of measuring or observing what happens to the electrons as they pass

through the slit had changed the outcome. An intuitive although slightly incorrect example of this would be something impossible like measuring something with your

eyes closed, yet after opening your eyes having the measurement be something different entirely.

This picture is a great example of the results of the experiment. The picture on the left shows the result with no measuring done. A diffraction pattern is observed and the electrons behave as a

wave. Yet with measurements done the electron forms a 2 band pattern and behaves as a particle.

• This experiment showed that electrons behave as both WAVES AND PARTICLES! This revolutionized the field of quantum mechanics.