Question

21) The two-slit experiment illustrated several fundamental concepts in quantum mechanics. Explain what each of these is and how they are demonstrated in the experiments:

1. Intrinsic Randomness
2. Measurements Affect Reality
3. Superposition
4. Heisenberg’s Uncertainty Principle

Answer 1

a. Intrinsic randomness: The inherent randomness of any system due to the lack of information thus indeterministic.

Each electron passes through one of the slits but we cannot say through which silt it passes through if we do not check when it passes through. Thus it is intrinsically random as we lack the information about the trajectory of that the particle follows through the slits.

b. Measurement affects reality: When any act of measurement changes the outcome.

If you try to know or look through which slit the electron is trying pass through then you affect the electron and thus you would not observe an interference pattern anymore. Which means that the moment you make a measurement, in this case interacting with the electron to know its position and trajectory, you affect its outcome i.e. its reality.

c. Superposition: The vector addition of the amplitude of the waves in space at any point is called superposition.

The interference pattern formed on the screen shows that electron acts like a wave as superposition is only shown in case of waves. If it were a particle the the pattern formed would be gaussian rather than interference pattern,

d. Heisenberg's Uncertainity principle: It states that position and velocity in quantum mechanics cannot be measured simultaneously. The uncertainity of both position and momentum is equals to half of planck's constant. In this case, we cannot know simultaneously which slits the electron passes through and get an interference pattern.

If the slit wall were to be movable in traverse direction then electron entering in any of the slits might kick the wall and make it in motion. From the wall's motion we can know from which slit the electron passed through and it would be contradictory of what we observed at the screen. That is we cannot know simultaneously which slits the electron passes through and still expect an interference pattern.