Question 1

What kind of spectra did the physicist Anders Jonas Ångström discover in his study of low-pressure gas discharge tubes?

Accepted Answer

A)  continuous 
B)  discrete 
C)  blackbody 
D)  band 
E)  dark-line

Question 2

Two lasers emit equal numbers of photons per second. If the first laser emits red light and the second emits blue light, the power radiated by the first is

Accepted Answer

A)  equal to that emitted by the second. 
B)  greater than that emitted by the second. 
C)  less than that emitted by the second. 
D)  dependent on the time interval of the emission.

Question 3

Electrons are accelerated through a potential difference of 90.0 kV and directed at a tungsten target to produce x-rays. What is the cutoff frequency of the x-ray spectrum produced?

Accepted Answer

A)  2.18 × 1019 Hz 
B)  2.10 × 1019 Hz 
C)  1.17 × 1021 Hz 
D)  9.25 × 1021 Hz 
E)  6.20 × 1015 Hz

Question 4

Light of wavelength 400 nm bombards a surface that has a work function of 2.46 eV. What is the maximum kinetic energy of the photoelectrons from this surface?

Accepted Answer

A)  No photoelectrons are emitted. 
B)  2.46 eV 
C)  3.30 eV 
D)  0.640 eV 
E)  0.840 eV

Question 5

What is the smallest energy photon that a hydrogen atom in the ground state can absorb?

Accepted Answer

A)  any energy 
B)  13.6 eV 
C)  10.2 eV 
D)  3.40 eV 
E)  1.90 eV

Question 6

What is the maximum wavelength photon that can produce a pair of tau particles (mass 1.777 GeV/c2) by pair production?

Accepted Answer

A)  8.72 × 10−8 nm 
B)  3.49 × 10−7 nm 
C)  6.98 × 10−7 nm 
D)  1.74 × 10−7 nm

Question 7

PET, the diagnostic method, stands for

Accepted Answer

A)  patterned electron technique. 
B)  positron emission tomography. 
C)  proton-electron transmission. 
D)  penetrating emission technique. 
E)  None of these choices are correct.

Question 8

Which of the following statements is true?

Accepted Answer

A)  All the photons of the Lyman series are in the ultraviolet. 
B)  Some of the photons of the Lyman series are in the visible. 
C)  Some of the photons of the Lyman series are in the infrared. 
D)  All the photons of the Balmer series are in the visible. 
E)  All these statements are false.

Question 9

Ultraviolet light is shone on a piece of metal, and electrons are observed to be ejected from the metal. The UV lamp is now replaced by a lamp of the same intensity, but which produces photons having a shorter wavelength. Which of the below differences is observed?

Accepted Answer

A)  More electrons per unit time are produced. 
B)  Nothing changes at all. 
C)  Electrons with a higher maximum energy are observed. 
D)  Electrons with lower maximum energy are observed.

Question 10

Which scientist proposed the nuclear model of the atom as a result of experiments involving alpha particle scattering?

Accepted Answer

A)  Albert Einstein 
B)  Niels Bohr 
C)  Ernest Rutherford 
D)  Max Planck 
E)  Richard Feynman

Question 11

Electrons are accelerated through a potential difference V and then strike a dense target. In the x-rays that are produced,

Accepted Answer

A)  the maximum wavelength depends on V. 
B)  the wavelengths of the characteristic peaks depend on V. 
C)  the minimum wavelength depends on V. 
D)  the speed of the x-rays depends on V.

Question 12

A Compton scattering experiment is performed in which the scattered photons have a minimum energy of 17.2 keV. What was the incident energy of the photons used in this experiment?

Accepted Answer

A)  16.6 keV 
B)  18.4 keV 
C)  16.1 keV 
D)  17.2 keV

Question 13

Monochromatic light shines on a surface that has a work function of 1.80 eV. The maximum kinetic energy of the emitted photoelectrons is 0.620 eV. What is the wavelength of the monochromatic light?

Accepted Answer

A)  200 nm 
B)  290 nm 
C)  689 nm 
D)  602 nm 
E)  512 nm

Question 14

X-rays of wavelength 0.240 nm are scattered from a free electron at rest and the resulting scattered photons have wavelength 0.244 nm. Through what angle did these photons scatter relative to the initial direction?

Accepted Answer

A)  130° 
B)  80° 
C)  such scattering is impossible 
D)  34°

Question 15

Photons of red light cause a surface to emit photoelectrons with maximum kinetic energy K(red). If photons of blue light of the same intensity are now used in the experiment, which of the following statements is true about the photoelectrons emitted (if any are emitted)?

Accepted Answer

A)  No photoelectrons are emitted. 
B)  maximum K(blue)  K(red) 
E)  None of these choices are true.

Question 16

If a hydrogen atom in the ground state absorbs a 20.0 eV photon, what kinetic energy of the electron results?

Accepted Answer

A)  this cannot happen 
B)  20.0 eV 
C)  13.6 eV 
D)  6.4 eV 
E)  33.6 eV

Question 17

Electrons are used to produce x-rays by allowing a beam of electrons to strike a heavy metal surface. When the speed of the electrons in the beam is increased, this produces

Accepted Answer

A)  x-rays with higher energies 
B)  x-rays with longer wavelengths 
C)  faster x-rays 
D)  more x-rays per unit time

Question 18

How many emission lines are possible for atomic hydrogen gas with atoms excited to the n = 4 state?

Accepted Answer

A)  1 
B)  2 
C)  4 
D)  5 
E)  6

Question 19

An x-ray tube produces photons with wavelengths down to a minimum of 0.0827 nm. What is the accelerating potential for this tube?

Accepted Answer

A)  123 kV 
B)  9.22 kV 
C)  8.00 kV 
D)  10.0 kV 
E)  15.0 kV

Question 20

A 2.00 eV photon has what frequency?

Accepted Answer

A)  6.40 × 1014 Hz 
B)  1.86 × 1014 Hz 
C)  3.15 × 1014 Hz 
D)  7.21 × 1014 Hz 
E)  4.84 × 1014 Hz

Exam 27: Early Quantum Physics and the Photon