Reading Assignments from 27 to 29

Spacetime coordinates

Combine location of an event and the time at which the event occurred

Two events are simultaneous

If they occur at the same time, regardless of observations.

How is the velocity, u', of an object as measured in a frame moving at v, related to the velocity of that object, u, as measured in a stationary reference frame?

u' = u-v

To accurately synchronize clocks at different positions in a reference frame

Account for time for signal from master clock to reach other clocks before starting them

An inertial reference frame is An inertial reference frame is

Moving at a constant velocity

Einstein's principle of relativity states

All physical laws are the same in all inertial reference frames.

Special relativity is used

Only in reference frames moving with a constant velocity, inertial reference frames

Which of these is not an inertial reference frame?

A plane accelerating for takeoff on a level runway.

The Galilean principle of relativity states

Newton's Laws of Motion are valid in all inertial reference frames.

Under what conditions is the speed of light 3x108 m/s (c = 3x108 m/s)?

In all inertial reference frames

Proper length is the length of an object as measured in

The frame the object is at rest in

How far does light travel in 1 second on a stationary light clock?

3x108 m

What is the resolution of the twin paradox?

The twin who stayed home measures the correct ages.

A light clock moving relative to you ticks slower than a light clock in your reference frame because

The light travels a larger distance

In section 5, what assumption does Peggy make which leads her to an incorrect conclusion?

That the two events were simultaneous in her reference frame.

A light clock

Uses the speed of light to measure time.

Evidence for time dilation includes

Atmospheric muons and GPS satellite corrections.

The proper time between two events is the time interval measured

When the events happen at the same position (measured with 1 clock)

Length contraction of an object is measured

For the dimension parallel to the motion.

How does the momentum of an object moving at close to c compare to the Newtonian velocity calculation?

More

What happens to the missing mass when the nucleus of an atom of uranium-235 fissions?

It is converted into kinetic energy

Momentum conservation is one of the main ideas of kinematics. Does it still hold true in special relativity?

Yes, if momentum is defined as γmu.

A student passes Earth flying in a rocket at 0.9c and shines a laser toward the front of the rocket. Another student on Earth watches as the rocket flies by. How fast does the Earth-bound student see the light from the laser moving?

C

The rest energy of an object

Is equal to mc2.

The relativistic velocity addition equations appear to be very different from the Galilean equations. Are they still applicable to non-relativistic speeds?

Yes. These equations can be used in all circumstances.

The speed of light is the speed limit of

Any causal influence (anything)

What is a positron?

The antimatter version of the electron

The equivalence of mass and energy says

Mass can be created from energy and energy can be created from mass

Conservation of energy

Explains energy released in nuclear fission

The maximum kinetic energy of an electron emitted due to the photoelectric effect is

Equal to the electron's energy in the atom minus the work function

One conclusion from Einstein's explanation for the photoelectric effect is

Each photon delivers all of its energy to one electron

X-rays can be used to image the bones in a body. What properties of materials make them effective at stopping X-rays?

High atomic number

X-ray diffraction is used to study the structure of

Proteins and Crystals

Strong x-ray reflection at specific angles of incidence is called

X-ray diffraction

In the photoelectric effect, electrons are emitted from a substance

For all frequencies of light above a threshold

The minimum amount of energy needed to free an electron from an atom is called

The work function

In photoelectric effect experiments, if the potential difference between the anode and cathode is equal to the stopping potential

All emitted electrons are pulled back to the cathode

Einstein's light quantum idea says

-The energy of a light quantum us proportional to its frequency

-Light moves as small bundles of energy

-Light is not a continuous wave

The energy of a quantum of light, a photon, can be expressed as

E = hf

A double slit experiment using very low light levels demonstrates

Both the wave and photon nature of light

The de Broglie wavelength is

The wavelength of a moving object

Electron microscopes have better resolution than visible light microscopes because

The electron wavelength is shorter than the visible light wavelength

Which of these is something many people possess which uses the photoelectric effect?

Digital camera (i.e., on a smart phone)

What is the velocity, v, of an electron with a de Broglie wavelength λ?

v = h/(mλ)

The quantized energy of a particle in a box depends on

The size of the box and the mass of the particle

Due to the wave nature of matter, a confined particle has

Quantized momentum and energy

In a double slit experiment with very low light levels, the interference pattern

Builds up over time

Diffraction patterns can be created with

X-rays

Neutrons

Electrons

Which of these can be used to produce wave phenomena like interference and diffraction patterns?

-Large molecules

-Atoms

-Neutrons

The uncertainty principle says

A precise location measurement increases the uncertainty in the velocity

Quantum jumps of an atom refer to

The allowed energy changes of electrons in an atom

The speed of an electron and a proton are measured to the same uncertainty. Which has a smaller uncertainty in position?

Proton, it is more massive

Which energy level of a quantum system is stable?

The lowest

The quantized energies of electron in atoms explains

Emission and absorption spectra of atoms

The emission spectra of different gases

Are completely different

A standing particle wave in a box has a lowest energy of 6 eV. Which of the following is not a possible energy level?

36 eV

How do electrons move between energy levels in a 1-dimensional box?

Quantum jumps

Tunneling is defined as

The wave nature of electrons allowing them to cross a gap

The lowest electron energy level of an atom is

Stable

The Balmer formula explains

The relation between the lines of the hydrogen spectrum

The Bohr model of the atom explains

-Stable atoms

-Emission spectra

-Absorption spectra

-Difference in the spectra of different elements

What problem did the Rutherford atomic model have that Bohr solved?

Electrons could radiate all their energy and spiral into the nucleus

To observe a discrete (line) spectrum the substance creating the spectrum must be

Gas

The atomic number of an atom is

The number of protons and electrons in a neutral atom

Early evidence that atoms are not indivisible came from experiments using

Alpha and beta rays

Is there a difference between absorption and emission spectra for an element in a gaseous form?

Yes. The emission spectrum has more lines.

The mass number of an atom is equal to

The number of protons plus neutrons in the nucleus.

What kind of force occurs between an alpha particle and the nucleus of an atom?

A repulsive electrical force

Rutherford's alpha experiment led to the

Nuclear model of the atom

How many de Broglie wavelengths fit in an electron's orbit in an atom?

n, where n = 1, 2, 3, ...

The combination of quantized energy levels and the Pauli exclusion principle explain

The entire structure of the periodic table

The Bohr hydrogen atom does not correctly predict

Atomic angular momentum

Which subshell has energy between the 4s and 4p subshells?

3d

Transitions down to which energy level produce visible light in the hydrogen emission spectrum?

n = 2

When an electron in an atom is treated as a de Broglie wave what is quantized?

Velocity of the electron

Radius of the orbit

Energy of the electron

Bohr's model for the hydrogen atom only needs one quantum number. How many quantum numbers are needed in Schrodinger's analysis of the hydrogen atom?

4

How many electrons are allowed in the 2p subshell?

6

The Pauli exclusion principle says

No 2 electrons can have the same set of quantum numbers.

If the principal quantum number, n, is equal to 2, what are the possible values for the orbital quantum number, l?

0, 1

The first row of transition elements (atomic number 21-30) is due to the filling of which suborbital?

3d

Which of these is a medical use of a laser?

Scalpel

Killing cancer cells

Vaporizing plaque in an artery

Do emission spectra have any constraints on the possible transitions?

Yes, the change in l must have a magnitude of 1 (Δl = ±1)

Coherent light is electromagnetic waves with the same

Direction

Phase

Amplitude

How do the wavelengths a molecule can absorb and the wavelengths a molecule can emit compare to each other?

Absorption wavelengths are shorter than emission wavelengths

Which of the following is not a property of a laser?

The light is in one direction

The light all has the same phase

The light is one wavelength

An additional rule for the allowed transitions in an absorption spectrum is

The transition must to a p orbital (l = 1)

What property of light allows a laser beam to travel down an optical fiber?

Total internal reflection

What is the constraint on the transition when an electron collides with an atom causing the atom to transition to a higher energy state?

Energy must be conserved

Compared to atoms, the energy levels of molecules

Are large in number and very close together.