# Quantum mechanics/Course/Wave-particle duality quiz

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## Wave particle duality quiz version A

1 The first (particle) segment in Wave-particle duality.ogv does not depict a diffraction pattern when particles impinge upon two slits because particles are never observed to exhibit diffraction.

 true false

2 The first (particle) segment in Wave-particle duality.ogv does not depict a diffraction pattern when particles impinge upon two slits because classical (Newtonian) physics fails to predict such diffraction.

 true false

3 The second (wave) segment of Wave-particle duality.ogv depicts a two slit diffraction pattern that is modeled by a formula put forth by

 Schroedinger in 1926. Newton in 1704. Taylor in 1909. Young in 1801. Heisenberg in 1925.

4 The (wave) second segment of Wave-particle duality.ogv is based on the fact that the two waves emanating from the two slits can interfere with each other.

 true false

5 Observe the second (wave) segment of Wave-particle duality.ogv and note the rapid divergence of the wave at each of the two slits (better seen here). This occurs because significant single slit diffraction occurs for a slit that is sufficiently wide.

 true false

6 Observe the second (wave) segment of Wave-particle duality.ogv and note the rapid divergence of the wave at each of the two slits (better seen here). This occurs because significant single slit diffraction occurs for a slit that is sufficiently narrow.

 true false

7 A "spooky" variation of the third (quantum) segment of Wave-particle duality.ogv occurs when the signal is so weak that only one particle is usually near the slit at any given time. This experiment was first performed by

 Davisson and Germer in 1925. Newton in 1704. Taylor in 1909. Aspect in 1982. Young in 1801.

8 An understanding of the diffraction pattern associated with particles is based on

 Forces that the De Broglie pilot wave exert on individual particles. Interference between the component of the wave from each slit. Forces that the De Broglie pilot wave exert between pairs of particles. All of these nearly equivalent models explain diffraction. The fact that particles can make glancing collisions with the edge of a slit.

9 An observer is present is the fourth segment of Wave-particle duality.ogv. This observer disrupts the diffraction pattern because:

 By the uncertainty principle, knowing that the particle is near one slit constitutes a measurement that causes uncertainty in the particle's future motion. While all of these arguments have been used, the validity of some are "uncertain"(pun intended). By the Copenhagen interpretation, knowing that the particle is in one slit destroys the wavefunction at the other slit. If Heisenberg's microscope is used to ascertain which slit has the particle, the wavelength required to obtain sufficient resolution implies that the photons have sufficient individual momentum to "kick" the particle out of its original path.

10 A dead "fly" of mass $m$ is placed in a dark gravity-free vacuum, somewhere not too far from the origin. The speed of the fly is known to be zero with virtually zero uncertainty. To ascertain the fly's position you construct "flyswatter" that can detect any collision between the flyswatter" and fly. A small hole of radius $\Delta x$ in the center of the flyswatter will inform you of whether a collision took place. The uncertainty in the fly's position is $\Delta x$ if the fly passed through the hole. The fly's (non-relativistic) speed is now unknown but estimated to be zero with an uncertainty that can be calculated from:

 $m\Delta v\cdot \Delta x\geq {\frac {\hbar }{2}}$ $\Delta v\cdot \Delta x\geq {\frac {m\hbar }{2}}$ $\Delta v\cdot \Delta x\leq {\frac {m\hbar }{2}}$ $m\Delta v\cdot \Delta x\leq {\frac {\hbar }{2}}$ 