Chapter 15 Review

Video Review

Key Concept Summary

TA Summary

Vocabulary

Describes the likelihood of detecting a particle as it travels through space

The more you know about position the less you can know about momentum, and the more you know about momentum the less you can know about position.

Phenomenon that creates areas of high probability where the electron will strike the screen

Phenomenon that creates areas of low probability where the electron is unlikely to strike the screen

Postulates a universe where actions do not lead to pre-determined effects

The physical world continues on a predetermined course once set in motion.

Alternating bands of regions where lots of electrons shot at closely spaced slits hit a screen followed by regions where no electrons hit the screen.

True/False

The uncertainty principle states that the more you know about position, the more you know about momentum.

True False

Matter has both wave and particle properties.

True False

Electrons can form interference patterns, just as light can.

True False

It is impossible to predict exactly where an electron will strike the screen after passing through two slits in a double-slit experiment.

True False

An object's momentum is the only property associated with probability waves.

True False

If moving slowly enough, small objects can have wavelengths that reach macroscopic dimensions.

True False

After passing many electrons through two slits, an interference pattern on the screen looks like the probability curve below.

True False

Analysis

If the speed of a particle increases, its wavelength

decreases. increases. stays the same. could increase, decrease, or stay the same.

Which of the following could NOT be caused to form a diffraction pattern?

visible light x-rays ultraviolet light electrons none of the above; all could form diffraction patterns

For which phenomenon would the Heisenberg Uncertainty Principle be a significant consideration in describing motion?

Electrons in atoms. Planets in orbit around the sun. Space shuttle in orbit around the earth. Billiard balls on a pool table. Brownian motion of dust particles

Macroscopic objects don't show interference effects because

quantum mechanics doesn't apply to big objects. they are larger than the wavelength of light. their wavelengths are too short. they can't fit through small slits. they don't have wave properties. the Heisenberg Uncertainty Principle doesn't apply to them.

The Heisenberg Uncertainty Principle seems to conflict with the concept of

operationalism the quantum theory Newtonian determinism duality mass

Electrons passing one at a time through a two-slit apparatus strike a screen. The resulting pattern on the screen after many electrons have struck the screen is

a single band of points about as narrow as one slit. a single broad band of points, i.e., broader than the combined width of the slits. a completely random pattern of points. two narrow bands of points about the width of each slit. a pattern of bands where electrons hit separated by areas where no electrons hit.

If electrons orbit the nucleus of an atom, as the Bohr model suggests which of the following events should happen, but doesn't?

The atoms would continuously produce electromagnetic radiation. The atoms would produce a continuous emission spectrum all the time. The atoms would only produce one emission line. The electrons would collide with each other.

Which of the following electrons would have a larger wavelength?

the one with the fastest speed the one with the slowest speed the one with the smallest mass all electrons have the same wavelength.

An electron an a proton both have the same momentum, which has the larger wavelength?

the electron the proton the wavelengths are the same.

Why don't we observe wave behavior in macroscopic objects like baseballs?

Their mass is too large. Their speed is too small. Their position can be measured too accurately. They are not charged.

How does the wavelength of an electron compare to the wavelength of electromagnetic waves?

Electrons have smaller wavelengths. Electromagnetic waves have smaller wavelengths. The wavelengths are the same. The question makes no sense; any wavelength is possible for either.

What is the smallest object you could see with an electron microscope?

a single cell a large molecule. an atom a proton.

By designing better and better instruments, it is possible to continue to improve the accuracy of measurements of the position of an electron indefinitely.

True False

By designing better and better instruments, it is possible to continue to improve the accuracy of measurements of an electrons trajectory (path through space as a function of time) indefinitely.

True False

The three dimensional wave function for an electron with quantum numbers n=2 and l=1 is depicted below. Dark regions are regions of high probability, where light regions are regions of low probability. What does this wave function mean? A depiction of a dumbell-shaped orbital with two lobes.

A depiction of a dumbell-shaped orbital with two lobes.

The electron follows a path that is shaped like a figure eight. The electron itself is shaped like a figure eight. The electron has a high probability of being detected. If you try to measure the electron's position you are most likely to find it somewhere in the figure eight.

Which of the following is a consequence of the Pauli exclusion principle?

That electron wave functions don't overlap. The electron wave functions all have a different size or shape. That electrons in higher energy levels must be farther from the nucleus than electrons in lower energy levels. That an electron is never in the nucleus of an atom. No two electrons can share exactly the same state

Free Response

Explain how the double-slit experiment can show both the particle and wave nature of matter.
A proton has a mass that is about 2,000 times as large as the mass of an electron. If a proton and an electron are traveling the same speed, which one will have the larger wavelength?
In an experiment called the Stern-Gerlach experiment, a silver atom passing through a magnet will either bend up or bend down. Quantum mechanics can be used to predict the probability of it going up or down, but not what a single atom will do on a trip through the magnet. What experiment could you do to test whether the probabilities predicted by quantum mechanics are correct?
Very slow neutrons can have wavelengths as long as a millimeter. Use the Heisenberg Uncertainty Principle to explain what a beam of these neutrons will look like after passing through a hole a few millimeters in diameter.
How does the wavelength of an electron in an atom compare to an electron which is moving much faster in a particle accelerator?
Can a single proton interfere with itself? Why or why not?
Your friend argues that she has no choice in her life because the Heisenberg Uncertainty Principle guarantees that everything in this life is random. How would you respond to her?
Physicists have recently been able to slow down beams of atoms so that their wavelengths are macroscopic in size. Under these conditions would it be possible to see interference effects with this beam of atoms? Why or why not?