## SAT Physics Subject Test

**Chapter 16 ****Modern Physics**

**Chapter 16 Review Questions**

See __Chapter 17__ for solutions.

__1.__ Which of the following best approximates the energy of a photon whose wavelength is 2.0 nm? (Planck’s constant, *h*, has a value of 6.6 × 10^{–34} J • s.)

(A) 4 × 10^{–51} J

(B) 1 × 10^{–34} J

(C) 1 × 10^{–16} J

(D) 1 × 10^{34} J

(E) 2 × 10^{–50} J

__2.__ A metal whose work function is 6.0 eV is struck with light of frequency 7.2 × 10^{15} Hz. What is the maximum kinetic energy of photoelectrons ejected from the metal’s surface?

(A) 7 eV

(B) 13 eV

(C) 19 eV

(D) 24 eV

(E) No photoelectrons will be produced.

__3.__ An atom with one electron has an ionization energy of 25 eV. How much energy will be released when the electron makes the transition from an excited energy level, where *E* = –16 eV, to the ground state?

(A) 9 eV

(B) 11 eV

(C) 16 eV

(D) 25 eV

(E) 41 eV

__4.__ The single electron in an atom has an energy of –40 eV when it’s in the ground state, and the first excited state for the electron is at –10 eV. What will happen to this electron if the atom is struck by a stream of photons, each of energy 15 eV?

(A) The electron will absorb the energy of one photon and become excited halfway to the first excited state, then quickly return to the ground state, without emitting a photon.

(B) The electron will absorb the energy of one photon and become excited halfway to the first excited state, then quickly return to the ground state, emitting a 15 eV photon in the process.

(C) The electron will absorb the energy of one photon and become excited halfway to the first excited state, then quickly absorb the energy of another photon to reach the first excited state.

(D) The electron will absorb two photons and be excited to the first excited state.

(E) Nothing will happen.

__5.__ What is the de Broglie wavelength of a proton whose linear momentum has a magnitude of 3.3 × 10^{–23} kg • m/s ?

(A) 0.0002 nm

(B) 0.002 nm

(C) 0.02 nm

(D) 0.2 nm

(E) 2 nm

__6.__ Compared to the parent nucleus, the daughter of a β^{–} decay has

(A) the same mass number but a greater atomic number

(B) the same mass number but a smaller atomic number

(C) a smaller mass number but the same atomic number

(D) a greater mass number but the same atomic number

(E) None of the above

__7.__ The reaction is an example of what type of radioactive decay?

(A) alpha

(B) β^{–}

(C) β^{+}

(D) electron capture

(E) gamma

__8.__ Tungsten-176 has a half-life of 2.5 hours. After how many hours will the disintegration rate of a tungsten-176 sample drop to its initial value?

(A) 5

(B) 8.3

(C) 10

(D) 12.5

(E) 25

__9.__ What’s the missing particle in the following nuclear reaction?

(A) Proton

(B) Neutron

(C) Electron

(D) Positron

(E) Deuteron

__10.__ What’s the missing particle in the following nuclear reaction?

(A) Proton

(B) Neutron

(C) Electron

(D) Positron

(E) Gamma

__11.__ Two spaceships are traveling directly toward each other, one traveling at a speed of and the other at a speed of , as measured by observers on a nearby planet. The faster ship emits a radar pulse directed toward the approaching ship. What is the speed of this radar pulse, as measured by observers on the planet?

(A)

(B)

(C) *c*

(D)

(E)

__12.__ An Imperial battle cruiser, sitting in a hanger deck, is measured to have a length of 200 m by a worker on the deck. If the cruiser travels at a speed of *c* past a planet, what will be the length of the cruiser, as measured by the inhabitants of the planet?

(A) 0

(B) Between 0 and 200 m

(C) 200 m

(D) Greater than 200 m

(E) None of the above, since it is impossible to reach the described speed

__13.__ An astronaut lives on a spaceship that is moving at a speed of *c* away from the earth. As measured by a clock on the spaceship, the time interval between her maintenance checks on the ship’s main computer is 15 months. In the reference frame of the team here on Earth that monitors the ship’s progress, what is the time interval between maintenance checks on the ship’s main computer?

(A) Always less than 15 months

(B) Always exactly 15 months

(C) Always more than 15 months

(D) Initially less than 15 months, but after time more than 15 months

(E) Initially more than 15 months, but after time less than 15 months

__14.__ A particle whose rest energy is *E* is traveling at a speed of *c*. What is the particle’s kinetic energy?

(A)

(B)

(C)

(D)

(E)

__15.__ Redshift of distant galaxies is evidence for which of the following?

(A) Expansion of the universe

(B) The Uncertainty Principle

(C) Black holes

(D) Dark matter

(E) Superconductivity

__16.__ Which of the following is NOT a correct pairing of physicist and field in which he made significant contributions?

(A) Newton — gravitation

(B) Einstein — relativity

(C) Faraday — electricity and magnetism

(D) Coulomb — quantum mechanics

(E) Bohr — atomic structure

__17.__ The impossibility of making simultaneous, arbitrarily precise measurements of the momentum and the position of an electron is accounted for in

(A) thermodynamics

(B) quantum mechanics

(C) classical electrodynamics

(D) special relativity

(E) general relativity

**Keywords**

raisin pudding model

alpha particles

Rutherford nuclear model

quanta

photon

photoelectric effect

photoelectrons

threshold frequency

Planck’s constant

work function

electronvolt (eV)

atomic spectra

excited

energy level

quantized

wave–particle duality

de Broglie wavelength

protons

neutrons

nucleons

atomic number

neutron number

mass number

nucleon number

isotopes

nuclide

strong nuclear force

atomic mass unit (amu)

dueteron

deuterium

mass defect

binding energy

mass–energy equivalence

radioactive

alpha

beta (β)

gamma

parent

daughter

electron capture (Ec)

beta particle

electron-antineutrino

weak nuclear force

positron

antiparticle

electron-neutrino

gamma ray

decay constant

activity

becquerel (Bq)

half-life

exponential decay

nuclear fission

nuclear fusion

disintegration energy

exothermic

endothermic

inertial reference frame

relativistic factor

length contraction

rest energy

total energy

general relativity

Equivalence Principle

precession of Mercury

gravitational time dilation

black hole

quasar

expansion of the universe

electron microscope

Heisenberg Uncertainty Principle

superconductor

weak nuclear force

Cosmic Microwave Background

dark matter

dark energy

**Summary**

For the test, be sure you are familiar with the following concepts from this chapter.

· Rutherford model of the atom

· Photons and the photoelectric effect

· The Bohr model of the atom

· Wave–particle duality

· Nuclear physics

· The nuclear force

· Binding energy

· Radioactivity

· Alpha decay

· Beta decay

· β^{–} decay

· β^{+} decay

· Electron capture

· Radioactive decay rates

· Nuclear reactions

· Disintegration energy

· Special relativity

· The relativity of velocity

· The relativity of time

· The relativity of length

· Relativistic energy

In addition, be able to describe the following briefly:

· General relativity

· Quantum mechanics

· Current problems in physics and astronomy