7 đề thi vật lý 2 Đại học Bách khoa TPHCM chương trình dạy bằng tiếng anh

NATIONAL UNIVERSITY – HO CHI MINH CITY
UNIVERSITY OF TECHNOLOGY

FINAL EXAM OF PHYSICS A2
SEMESTER 1, YEAR 2015-2016
Closed book exam – Duration: 120 min

Code:

138

DEPARTMENT OF ENGINEERING PHYSICS

Student’s name:………………………………………..

Signature of Lecturer: ………………………………..

Student ID: ………………………………………………..

Signature of Dean: ……………………………………..

01. ; / = ~

06. ; / = ~

11. ; / = ~

16. ; / = ~

02. ; / = ~

07. ; / = ~

12. ; / = ~

17. ; / = ~

03. ; / = ~

08. ; / = ~

13. ; / = ~

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20. ; / = ~

PART 1. MULTIPLE CHOICE QUESTIONS
Question 1. In the Zeeman effect, the following selection rules are applied:
A.   1; m  1
B.   1; m  0,1 C.   0 1; m  1 D.   0 1; m  0,1
Question 2. In order of increasing strength the four basic interactions are:
A. gravitational, weak, electromagnetic, and strong
B. weak, gravitational, electromagnetic, and strong
C. weak, electromagnetic, gravitational, and strong
D. gravitational, electromagnetic, weak, and strong
Question 3. For valence electrons in atoms of sodium Na (Z=11), while taking into account of the spin,

electrons can make the transition to energy level 32 D3 / 2 from the following energy levels:
A.

n 2P1/ 2 (n  4,5,6...); n 2P3 / 2 (n  4,5,6...);n 2F7 / 2 (n  4,5,6...)

B.

n 2 P1/ 2 (n  4,5,6...);n 2 P3 / 2 (n  4,5,6...);n 2 F5 / 2 (n  3,5,6...)

2
2
2
C. n P1/ 2 (n  4,5,6...);n P3 / 2 (n  4,5,6...);n F5 / 2 (n  4,5,6...)
2
2
2
D. n P1/ 2 (n  4,5,6...);n P3 / 2 (n  4,5,6...);n F7 / 2 (n  3,5,6...)

Question 4. Electromagnetic radiation with a wavelength of 5.7×10

−12

m is incident on stationary
electrons. Radiation that has a wavelength of 6.57×10−12 m is detected at a scattering angle of:
A. 50◦
B. 25◦
C. 40◦
D. 69◦
Question 5. A particle in an infinite potential energy well of width a. The particle is at the state of n=5.
The probability of finding particle in the region [a/10, 4a/5] is:
A. 0.8
B. 0.4
C. 0.3
D. 0.7
Question 6. When a hydrogen atom makes the transition from the third excited state to the ground state
(at−13.6 eV) the energy of the photon emitted is:
A. 9.1eV
B. 1.5eV
C. 12.1eV
D. 12.75eV
65
Question 7. Given Ro=1.2fm . The radius of 29
Cu nucleus is :
A. 4.8 fm
B. 3.8 fm
C. 5.8 fm
D. 6.8 fm
Question 8. The quark content of a proton is:
Code 138 / Page 1 of 4

A. uud
B. ddd
C. uuu
D. udd
Question 9. A particle is confined by finite potential energy walls to a one-dimensional trap from x=0 to

x=L. Its wave function in the region x<0 has the form (with k is positive):
A. ψ(x)=0
B. ψ(x)=Aexp(−kx) C. ψ(x)=Asin(kx)
D. ψ(x)=Aexp(kx)
Question 10. A meter stick moves in the direction of its length through a laboratory. According to
measurements taken in the laboratory, its length is 0.4 m The speed of the meter stick relative to the
laboratory is:
A. 0.95c
B. 0.96c
C. 0.92c
D. 0.31c
Question 11. A measurement of the length of an object that is moving relative to the laboratory consists
of noting the coordinates of the front and back:
A. at the same time according to clocks that move with the object
B. at different times according to clocks at rest in the laboratory
C. at the same time according to clocks at rest with respect to the fixed stars
D. at the same time according to clocks at rest in the laboratory
Question 12. Which of the following particles has a lepton number of zero?
A. νe
B. p
C. µ+
D. e+

Question 13. An electron is in a one-dimensional trap with zero potential energy in the interior and
infinite potential energy at the walls. A graph of its wavefunction ψ(x) versus x is shown. The value of
quantum number n is:

A. 2
B. 0
C. 4
D. 6
2
Question 14. The significance of || is:
A. energy density
B. energy
C. probability density D. probability
Question 15. An electron is in a quantum state for which there are seven allowed values of the z

component of the angular momentum. The magnitude of the angular momentum is:
B. 12
C. 9
D. 3
A. 7
Question 16. Two events occur simultaneously on the x axis of reference frame S, one at x=−a and the
other at x=+a. According to an observer moving in the negative x direction:
A. the event at x=−a occurs first
B. the event at x=+ a occurs first
C. the events are simultaneous
D. either event might occur first, depending on the value of a and the observer's speed
Question 17. The Balmer series of hydrogen is important because it:
A. is the only series that occurs for hydrogen
B. is the only one for which the quantum theory can be used
C. involves the lowest possible quantum number n

D. is in the visible region
Question 18. To a good approximation, the sun's surface is a blackbody with a surface temperature of
5800 K. The wavelength at which the sun emit most strongly is
A. 550nm
B. 500nm
C. 600nm
D. 450nm
Code 138 / Page 2 of 4


Question 19. Star S1 is moving away from us at a speed of 0.5c. Star S2 is moving away from us in the
opposite direction at a speed of 0.6c. The speed of S1 as measured by an observer on S2 is:
A. 0.85c
B. 0.5c
C. 0.93c
D. 1.3c
6
Question 20. An electron moves with a speed of 4.7 10 m / s . Its de Broglie wavelength is
A. 1.55 1010 m
B. 8.4 1012 m
C. 1.55 1012 m
D. 8.4 1014 m

PART 2. PROBLEMS
Problem 1
The ground-state wave function for hydrogen (a 1s state) is

1s 

1

a 3

r

e r / a

r+dr

a) The probability that the electron will be found in the volume dV bounded by a
spherical shell of radius r and r+dr
b) The probability that the electron will be found in the volume V from r=0 to r=a from the nucleus?
b) What is the probability that the electron will be found in a region from r=0 to r= from the nucleus?
Where a = 0.53x10-10m
Problem 2
Find the total binding energy and the binding energy per nucleon of 197
79 Au . The neutral atomic mass of
197
79 Au is

196.966569 u. The mass of neutron is mn=1.008665u, the mass of Hydrogen atom is
mH=1.007825u. The atomic mass 1u=931.5MeV/c2.
Problem 3
A proton and an antiproton annihilate, producing two photons. Find the energy, and wavelength of each
photon
(a) if the p and p are initially at rest and
(b) if the p and p collide head-on, each with an initial kinetic energy of 900 MeV.

Some physical constants
Stefan-Boltzmann constant: =5,67.10-8 W/(m2K4)
Wien constant:

b=2,898.10-3 (m.K)
Compton wavelength of electron: o=2,426.10-12 (m)

e
 9.27 1024 (J / T)  5.79 105 eV / Tesla
2me
e
Nuclear magneton:  n 
 5.0507810 27 J / T
2mp
Bohr magneton: B 

The z component of the spin magnetic moment of the proton sz proton  2.7928 n

Code 138 / Page 3 of 4


Code 138 / Page 4 of 4


National University – Ho Chi Minh City
University of Technology
Department of Engineering Physics

FINAL EXAM OF PHYSICS A2 – SEMESTER 183
Closed book exam – Duration: 90 min

Student’s name:

No. 2

Student ID:

A) (L.O.1, L.O.2) MCQ ANSWER SHEET: (4 POINTS)

Choose for each question only one correct answer and darken corresponding circle in the following answer sheet.

1
2
3
4
5

A
O
O
O
O
O

B
O
O
O
O
O

C
O
O

O
O
O

D
O
O
O
O
O

6
7
8
9
10

A
O
O
O
O
O

B
O
O
O
O
O

C
O
O
O
O
O

D
O
O
O
O
O

11
12
13
14
15

A
O
O
O
O
O

B
O

O
O
O
O

C
O
O
O
O
O

D
O
O
O
O
O

16
17
18
19
20

A
O
O
O
O

O

B
O
O
O
O
O

C
O
O
O
O
O

D
O
O
O
O
O

1. An electron in an atom has a minimum uncertainty in position of 0.2 nm. If it is doubled to 0.4 nm by what factor does the
minimum uncertainty in momentum change?
A. Stays the same B. Factor of ¼
C. Factor of ½
D. Factor of 2
2. Neodymium 144Nd is a nuclide that undergoes alpha decay. The nuclide that is the product of the decay is
148

142
140
140
A.
Sm
B.
Ba
C.
Pr
D.
Ce
3. What is the de Broglie wavelength of an electron which is moving with speed of 4×104 m/s?
A. 17.3 nm
B. 26.5 nm
C. 12.9 nm
D. 18.2 nm
4. An electron is in the state with orbital quantum number l=5. What is the minimum angle of electron’s angular momentum and
0z axis?
A. 0.42 rad
B. 2.32 rad
C. 0.62 rad
D. 1.08 rad
5. Electromagnetic radiation with 0.75 MeV of energy is scattered from stationary electrons. The scattered photons have
wavelength equal to Compton wavelength. Through what angle were the photons scattered?
A. 0.54 rad
B. 2.46 rad
C. 3.21 rad
D. 0.82 rad
6. The concentration of photons in a uniform light beam with a wavelength of 500nm is 1.7 × 1013 m−3. The intensity of the beam
is:

A. 6.7 × 10−6 W/m2
B. 1.0 × 103 W/m2
C. 2.0 × 103 W/m2
D. 4.0 × 103W/m2
7. Which of the following electromagnetic radiations has photons with the greatest energy?
A. blue light
B. yellow light
C. x raysD. radio waves
8. Which of the following (n, l, m , ms) combinations is impossible for an electron in an atom?
A. 3, 1, 1, −1/2
B. 6,2,0,1/2
C. 3, 2, −2, −1/2 D. 3, 1, −2, 1/2
9. Which particle has the smallest rest energy?
A. A neutron
B. An electron
C. An ion

D. A proton

10. The electron microscope is a welcome addition to the field of microscopy because electrons have a __________________
wavelength than light, thereby increasing the ______________ of the microscope.
A. Longer; resolving power
B. Shorter; resolving power
C.Longer; intensity
D. Shorter; intensity
11. Find the excitation energy from the ground level to the third excited level for an electron confined to of an infinite square well
that has a width of 0.125 nm.
1/2

A. 361eV

B. 567eV

C. 167eV

D. 720eV

12. Compare the Broglie wavelength λe of an electron with the wavelength λp of a proton, if they have the same momentum.
A. λe < λp
B. λe > λp
C. λe = λp
13. An electron is in a quantum state for which there are 5 allowed values of the z component of the angular momentum. The
magnitude of the angular momentum
A. √3ħ
B. √6ħ
C. √5ħ
D. √12ħ
14. A radioactive source has a half-life of 100 days. If the initial activity is 1.0 mCi, what is the activity after 30 days?
A. 0.14 mCi B. 0.81 mCi
C. 0.55 mCi
D. 0.76 mCi
15. Protons in the nucleus attract electrons with enough electromagnetic force to keep them in orbit at high speeds. Protons in
general repel each other, but in the nucleus they are bound together. Why ?
A. The strong force binds the protons together on small distance scales.
B. The electrons orbiting the nucleus create an EM force on all sides due to their high speed of revolution.
C. The electroweak force binds the protons together on small distance scales.
D. The gravitational force binds the protons together on small distance scales.
16. An alien spacecraft is flying overhead at a great distance as you stand in your backyard. You see its searchlight blink on for
0.19s. The first officer on the spacecraft measures that the searchlight is on for 12ms. What is the speed of the spacecraft relative

to the earth expressed as a fraction of the speed of light c?
A. 12c
B. 0.19c
C. 0.998c
D. none of these.
17. The electron makes a transition from the n = 2 to n = 4 level by absorbing a photon. Calculate the wavelength of this photon.
A. 1024nm
B. 190nm
C. 486nm
D. 364nm.
18. The wave function of one particle moving along Ox axis is showed in Figure below. The wave function ψ(x) = 0 with x ≤ 0
and x ≥ 5. Calculate the probability for finding this particle in the area 3 ≤ x ≤ 5?

A. 50.5 %

B. 62.5 %

C. 25.5 %

D. 12.5 %

19. In Compton effect, the maximum kinetic energy of the emitted electrons is 3 keV. What's the wavelength of the incident light?
A. 0.3 Ǻ B. 0.5 Ǻ C. 0.6 Ǻ D. 0.4 Ǻ
20. An electron has energy of 15 eV. Define its frequency and the de Broglie wavelength.
A. 2.4 x 1015 Hz, 3.9 x 10-10 m
B. 2 x 1010 Hz,
3 x 10-12 m
15
C. 3.62 x 10 Hz, 0.317 x 10-9 m
D. No correct answer

B. PROBLEMS (L.O.1, L.O.2): (6 POINTS)
1. Energy radiated per second from 5 cm2 of the surface of a black-body is 36.75x103 J. Calculate:
a) The temperature of the body.
2/2


b) The wavelength of the radiation emitted with the greatest intensity.
Ans: T=6000K; Wavelength= 483 nm
2. An atom in a 3d state emits a photon of wavelength 475nm when it decays to a 2p state.
(a) What is the energy (in eV) of the photon emitted in this transition?
(b) Find the number of allowed transitions if the atom is now in an external magnetic field of 3,5T.
Ignore the effects of the electron’s spin.
(c) Calculate the photon energies (in eV) emitted in the case (b). Given Bohr magneton µB=
9.27x10-24 J/T.
Ans: a. 2,612eV; b. 9 transitions; c. (2.612 – 0.0002)eV; 2.612 eV; (2.612 + 0.0002)eV.
3. The common isotope of uranium, 238U, has a half-life of 4.47x109 years, decaying to
alpha emission.
(a) What is the decay constant?
(b) What mass of uranium is required for an activity of 1.00 Ci?
(c) How many alpha particles are emitted per second by 10.0 g of uranium?
Ans: λ=4.92x10-18, m=2.99x103kg, λN=1.24x105
Some useful constants:
h = 6,625.10 −34 J .s σ = 5,67.10 −8 Wm −2 K −4

me = 9,1.10

−31

kg

e = 1,6.10 −19 C

b = 2,898.10 −3 mK

1Ci = 3.7x1010 decays/s

3/2

c = 3.10 8 m / s

234

Th by


4/2


5/2


1
National University – Ho Chi Minh City
University of Technology
Department of Engineering Physics

FINAL EXAM OF PHYSICS A2
2018-2019
Closed book exam – Duration: 90 min

Student’s name:

No.

1

Student ID:

A) (L.O.1, L.O.2) MCQ ANSWER SHEET (4 pts):
Choose for each question only one correct answer and darken corresponding circle in the following answer sheet.

1
2
3
4
5

A
O
O
O
O
O

B
O
O
O
O

O

C
O
O
O
O
O

D
O 6
O 7
O 8
O 9
O 10

A
O
O
O
O
O

B
O
O
O
O
O

C
O
O
O
O
O

D
O
O
O
O
O

11
12
13
14
15

A
O
O
O
O
O

B
O
O

O
O
O

C
O
O
O
O
O

D
O
O
O
O
O

16
17
18
19
20

A
O
O
O
O
O

B
O
O
O
O
O

C
O
O
O
O
O

D
O
O
O
O
O

1. Einstein’s Postulates state that …
A. The laws of physics are the same in all inertial frames of reference.
B. The speed of light in vacuum is the same in all inertial frames of reference and is independent of the
motion of the source.
C. A particle can travel at the speed of light in vacuum.
D. Both A and B.
2. Planck assumed:
A. Energy can only be absorbed or released in tiny discrete packets, which are an integer multiple of a

quantum energy.
B. Quantum energy ε of an electromagnetic wave of wavelength λ is defined by the formula ε = hc / λ ,
where h is Plank constant and c is the speed of light in vacuum.
C. Both A and B.
D. None of these.
3. An alpha particle (m = 6.64 x10-27 kg) emitted in the radioactive decay of uranium-238 has an energy
of 4.20 MeV. What is its de Broglie wavelength?
A. 7.02 x10-15m
B. 5.67 x10-15m
C. 1.67 x10-15m
D. 7.20 x10-15m
4. An electron in an atom initially has an energy of -3.2 eV above the ground state energy. It drops to a
state with an energy of -5.5 eV above the ground state energy and emits a photon in the process. The
momentum of the photon is:
A. 1.2 x 10-27 kg.m/s
B. 1.7 x 10-27 kg.m/s
C. 4.3 x 10-27 kg.m/s
D. 2.3 x 10-27 kg.m/s
5. There are Uranium and Lead atoms in Uranium ore. Lead atoms are the products of the radiation of
Uranium. The half life of Uranium is 5.5×109 years. How old is the ore if the ratio between the number
of Uranium and Lead atoms are 5:1:
A.1.45 x 109 years
B. 4.47 x 109 years
6.02 x 108 years
8.02 x 1018 years
6. Einstein suggested that:
A. Light is composed of tiny particles called protons.
B. The speed of photon is c = 3.108 m/s in free space and equal v = c/n in medium
C. Each photon has energy ε = hc / λ , where h: Planck’s constant, λ : light wavelength
D. All of the above.

7. The wave function of a particle must satisfy certain feratures:
A. Must be a single-valued function.
B. Must be normalizable.
C. Must be a continuous function and the first derivative also must be continuous.


2
D. All of the above.
8. In Compton effect, the maximum kinetic energy of the emitted electrons is 3 keV. What's the
wavelength of the incident light?
A. 0.3 Ǻ
B. 0.5 Ǻ
C. 0.6 Ǻ
D. 0.4 Ǻ
9. In hydrogen atom, electron is in the quantum state 2s, received any energy to get the excited state.
What is the proper wave function of the excited state?
A. ψ511
B. ψ400
C. ψ500
D. ψ401
10. The binding energy of a nucleus is the energy that must be supplied to:
A. bind nucleons together in nucleus
B. remove an alpha particle
C. remove a beta particle D. separate the nucleus into nucleons
11. The half-life of a radionuclide is 60 days. After how many days will it decay to 0.1% of its original
activity?
A. 300 B. 600 C. 3000 D. 6000
12. The formulas of non-relativistic microscopic particle momentum is:
A. p = h/λ
B. p = (2mE)1/2

C. A and B are correct D. A and B are wrong
(For 02 next questions) A hydrogen atom in the 5g state is placed in a magnetic field of 0.600 T that is in
the z-direction.
13. Into how many levels is this state split by the interaction of the atom’s orbital magnetic dipole
moment with the magnetic field?
A. 10
B. 9
C. 8
D. 7
14. What is the energy separation between adjacent levels?
A. 5,1.10-5eV
B. 3,47.10-5eV
C. 3,6.10-5eV

D. 2,6.10-5eV

15. Which of the following (n, l, ml, ms) combinations is possible for an electron in an atom?
A. 3, 3, 1, −1/2
B. 6, 2, 0, 1/2
C. 3, 2, 3, 1/2
D. 3, 1, −1, 1
16. The frequency and wavelength of the matter wave associated with a 10eV free electron are:
A. 1.5 × 1034 Hz, 3.9 × 10−10 m
B. 1.5 × 1034 Hz, 1.3 × 10−34 m
15
−9
C. 2.4 × 10 Hz, 1.2 × 10 m
D. 2.4 × 1015 Hz, 3.9 × 10−10 m
17. Which of following statements is wrong :
A. ∆m = 0,±1 B. ∆l = ±1

C. ∆j = ±1
D. A and B are correct
(For 02 next questions) Two stars, both of which behave like ideal blackbodies, radiate the same total
energy per second. The cooler one has a surface temperature T and a diameter 3.0 times that of the hotter
star.
18. What is the temperature of the hotter star in terms of T?
A. 4T
B. 1.7T C. 2.04T D. 2T
19. What is the ratio of the peak-intensity wavelength of the hot star to the peak-intensity wavelength of
the cool star?
A. 0.4
B. 0.58
C. 4.04 D. 0.2
20. A radionuclide decays to a nuclide with the same A, and with Z increasing by 1. This is an example
of ……… decay.
A. Beta minus
B. Beta plus
C. Gamma
D. Alpha


3

B. PROBLEMS (L.O.1, L.O.2):
1. (2 pts) A black-body emits the radiation with the greatest intensity wavelength 0.550 μm. Calculate:
a) The temperature of the body.
b) The energy radiated per second from 10cm2 of the body surface.
Sol.
T :=b/.76e-6= 5269K
E := s*T^4*10e-4= 218522J

2. (2 pts) Electron in the Hydrogen has maximal angle between
cos α max = −3 / 2 3 .
a) What is the orbital quantum number l of mentioned electron state.
b) Find the possible values of L and Lz for this electron?
Sol.
l = 3; L = 2 3; Lz = 0, ±1, ±2, ±3

and the z-axis with

3. (1 pt) a) Calculate the minimum energy required to separate a tritium (3H) into its component parts
(1amu= 931.2 MeV), where mproton = 1.00727 amu, mneutron = 1.00866 amu, mtritium = 3.0161 amu.
b) Why should the fusion occur in the condition of very high temperature (~106 K) ?
Sol.
E= 7.9 MeV = 0.126e-11 J
4. (1 pt) A particle moving in one dimension (the x-axis) is described by the wave function
 Ae − bx , x ≥ 0
ψ (x) =  bx
 Ae , x < 0
where b = 2.00 m-1, A>0, and the +x-axis points toward the right.
a) Determine A so that the wave function is normalized.
b) Find the probability of finding this particle in each of the following regions: (i) within 50.0 cm of the
origin, (ii) on the left side of the origin, (iii) between x = 0.500 m and x = 1.00 m.
Sol.
A = sqrt(b) = sqrt(2) m-1
Some useful constants:
h = 6,625.10 −34 J .s
c = 3.10 8 m / s

σ = 5,67.10 −8 Wm −2 K −4
me = 9,1.10 −31 kg

b = 2,898.10 −3 mK
e = 1,6.10 −19 C


FINAL EXAM OFPHYSICS A2

NATIONAL UNIVERSITY- HO CHI MINH CITY

SEMESTER 2, YEAR 2015-2016

UNIVERSITY OF TECHNOLOGY

Closed book exam

- Duration:

120 min

Code: X.52

DEPARTMENT OF ENGINEERING PHYSICS

Qf

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Signature of Lecturer:

rrlant'

Signature of Dean:
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13.@ @ @

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15.@ @ @

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1s.@ @ o
1e.@ @ o
20.@ @ o

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06.@ @ @

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07.@ @

03.@ @ @

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04.@ @ @
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01.@ @ @

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PART

1.

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f.

...

o

MULTII'LE CIIOICE QUESTIONS

o

@
@
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17.@ @

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(5 points)

Question 1. An electron participates in:
A. the electromagnetic and gravitational forces only
B. the electromagnetic, gravitational, and weak forces only
C. the electromagnetic, gravitational, and strong forces only
D. the strong and weak forces onlY
then:
euestion 2.If awave function y for a particle moving along the x axis is normalized,

A. 0Y l0t=l

t

TrYl2 dt=1
-@

. _l*12 dx=1

D. AY

l}x=l

what scattering
euestion 3. A photon of wavelength 1.60 x10'12 m scatters from a free electron. For
the scattered photon?
angle does the iecoiling electron have kinetic energy equal to the energy of
D. 70.0o
C.40.0o

B. 60.0o
A. 50.0"
|flnunucleus is:
Question 4. Given \:1.2fm. The radius of
D' 6'0 fm
C' 6'8 fm
B. 5.0 fm
A. 7.0 fm
Question 5. Messenger particles of the strong interaction are called:
D' W andZ
. gluons
ssible values of the z component of orbital
.m2ls and -3.16 x10-34 kg,nf ls. The orbital

D'2
c.4
B. 1
A. 3
freld I Consider
euestion 7. A hydrogen atom in a 3p state is placed in a uniform external magnetic
moment. What field
the interaction of thetagnetic field with the atom's orbital magnetic dipole
with an energy difference
magnitude B (in Tesla) iirequired to split the 3p state into multiple levels
of 3.1x10-sey between adjacent levels?
D.0.54
c.0.59
A.0.49

8.0.64

Broglie wavelength is
D.t.ox1o-1om
c. l.gxlo-l4m
B. I .gx lo-12 m
A.8.4"10-lam
euestion 9. In the Zeeman effect, when the atom is put in an external magnetic field B, how many
possible transitions are there from the nD to the mP energy levels?
D.9
c.3
B.5
A.7
is:
Question 10. Evidence for the wave nature of matter
A. electron diffraction experiments of Davisson and Germer
B. Young's double slit experiment
c. Thompson's measurement of e/m
D. the Compton effect
Question 11. The quark content of a molecule CO (lf c;lfro; is:
D. 38u.40d
C.40t.42d
8.44u,46d
A.40u.38d
Question 12. Ameasurement of the length of an object that is moving relative to the laboratory
consists of noting the coordinates of the front and back:
A. at the same time according to clocks that move with the object
B. at the same time according to clocks at rest with respect to the fixed stars
C. at the same time according to clocks at rest in the laboratory
D. at different times according to clocks at rest in the laboratory

Question 13. The Heisenberg uncertainty principle for position and momentum is given by:
Question 8. An proton moves with a speed of

A.

All other answers

C. Lx.Lpr>

are

S.O x

correct.

l06m/s. Its

B.

de

l*.1px > *.
L

h

O. Ax.Anr

,

,h
>;

Question 14. . For valence electrons in atoms of sodium Na (Z:1 1), while taking into account of the
spin, the sharp spectral lines are the transitions:

A.32\tz-n2D312(n=3,5,6...),3'Pr,r-n2D312(n=3,5,6...),3'Pltz-nzD512(n=3,5,6...),
B.32Dltz-n2F512(n=4,5,6...),3'Dstz-n2F512(n=4,5,6...),3'Dr,r-n2f71;1^=4,5,6...),

c.

- n2P1 2(n = 3,5,6...)3' sr,, - n2P3 2(n = 3,5,6 "') ;
o- 32\12 -n2st.tz(n : 4,5,6...); 3'Prtr-nStl z(n= 4,5,6"'),
32 sr |

2

1

1

euestion 15. Let A be the mass number and Zbethe atomic number of
following is^approximately correct for light nuclei?
A.

Z-^2

B.

A.

F"e
+=-Sme

B.

Z:A

C.

il-= 2m^
+
------:-

c.

Z:24

a nucleus.

D.

Which of the

Z:N2

euestion 16. The total energy of a proton is twice its rest energy. The momentum'of the proton in
MeV/c units is
D.1.52x 103
c.1.62 x 10'

B.1.32 x 10'
A.1.42x 103
of electron is::
momentum
euestion lT.Theratio between spin magnetic moment and spin angular

Se

b=-*.
SeSZfr"

D.

+=-;'

euestion 18. A particle in an infinite potential energy well of width a. The particle is at the state of
n:6. The probability of finding particle in the region [a/6,3a/4]is:
D.2t3
c.5n2
8.7 n2
A.413
euestion 19. To a good approximation, the sun's surface is a blackbody with a surface temperature of
6000 K. The wavelength at which the sun emit most strongly is
D' 520nm

A.550nm

B.483nm

C.450nm

Question 20. An electron is in a one-dimensional well with finite potential energy barriers at the
walls. The matter wave:
B. extends into the barriers
A. is zero in the
D. is zero at the ba:riers
C. is discontinuous at the

well

barriers

PART 2. PROBLEMS (5 points)
PROBLEM 1(2 points)
A quantum particle has a wave function

.*(x)={f;.-.'*.0
a) Find the constant

A

x>o

so that the wave function is normalized.

b) Find the probability of finding the particle between

x:0

and

x:a

PROBLEM 2 (2 points)

A spacecraft is launched from the surface of the Earth with a velocity of 0.600c at an angle of 50.0o above the
horizontal positive x axis. Another spacecraft is moving past with a velocity of 0.700c in the negative x
direction. Find the magnitude and direction of the velocity of the first spacecraft as measured by the pilot of
the second spacecraft.

Problem 3 (1 points)
Protons are placed in a 3.50T magnetic field that points in the positive z direction.
(a) What is the energy difference between states with the z component of proton spin angular momentum
parallel and antiparallel to the field.
(b) A proton can make a transition from one of these states to the other by emitting or absorbing a photon with
the appropriate energy. Find the frequency and wavelength of such a photon.

Some phltsical constants

Stefan-Boltzmann constant:

Wien

constant:

e5,67. I 0{ W1m2K4;
b:2,898.10-'(m.K)

Compton wavelength of electron. Lo1,426.10-t2 1m;

Bohr magneton:

ps =

'

2^"
="h

Nuclear magneton: pn =

=9.27 xtl-241J lT) = 5.8x 10-seV/Tesla

*=
zmp

5.05078x 10-27

J

lf

Thezcomponent of the spin magnetic moment of the protonlPszlproton =2.79281t'n

Paee 3

of3

National University – Ho Chi Minh City
University of Technology
Department of Engineering Physics

FINAL EXAM OF PHYSICS A2
2015-2016
Closed book exam – Duration: 120 min

Student’s name:

Student ID:

A) MCQ ANSWER SHEET:
Choose for each question only one correct answer and darken corresponding circle in the following answer sheet.

1
2
3
4
5

A
O
O
O
O
O

B
O

O
O
O
O

C
O
O
O
O
O

D
O
O
O
O
O

6
7
8
9
10

A
O
O
O
O

O

B
O
O
O
O
O

C
O
O
O
O
O

D
O
O
O
O
O

11
12
13
14
15

A

O
O
O
O
O

B
O
O
O
O
O

C
O
O
O
O
O

D
O
O
O
O
O

16
17
18

19
20

A
O
O
O
O
O

B
O
O
O
O
O

C
O
O
O
O
O

D
O
O
O
O
O

Some useful constants:
h  6,625.1034 J .s
c  3.108 m / s

  5,67.108 Wm 2 K 4
me  9,1.1031 kg

b  2,898.103 mK

e  1,6.1019 C

1. Consider the photoelectric effect for platinum
which is a metal with work function 8.50 eV.
What is the maximum wavelength of light λ max
that can be used to eject electrons from the metal?

A. 8.8 × 10-6 eV
B. 1 eV
C. 2 eV
D. 3.5× 10-5 eV

A. 176 nm
B. 225 nm
C. 145 nm
D 589 nm

4. In Compton scattering from stationary electrons
the largest change in wavelength occurs when the
photon is scattered through:

2. Assuming your cellular phone operates at 850
MHz, how many photons per second correspond
to 800 mW (a typical cell phone output strength)?
[FYI: The FCC mandates less than 1.6 W per
kilogram of tissue.]
A.
B.
C.
D.

76 s-1
0.185 × 1037 s-1
1.06 × 1024 s-1
1.06 × 1020 s-1

3. In Compton effect, the wavelength of the
incident light is 413 nm. What's the maximum
kinetic energy of the emitted electrons?

A. 0o
B. 45o
C. 90o
D. 180o
5. Electromagnetic radiation with a wavelength of
3.5 x 10-12 m is scattered from stationary electrons
ad photons that have been scattered through 50o
are detected. After a scattering event the
magnitude of the electron’s momentum is:
A. 1.5 x 10-22 kg.m/s

C. 2.2 x 10-22 kg.m/s

B. 2.0 x 10-22 kg.m/s
D. 8.7 x 10-23 kg.m/s

.

6. A material illuminated with 400-nm light is
observed to yield a photoelectric current for


stopping voltages less than 1.7 V. Now a new
monochromatic light source is used, and current is
observed for stopping voltages less than 1.0 V.
What is the wavelength of the new light source?

B. n = 5, l = -1, ml = 2
C. n = 3, l = 1, ml = -2
D. n = 2, l = 3, ml = -2
11. An electron in an atom initially has an energy
-3.2 eV above the ground state energy. It drops to
a state with an energy of -7.5 eV above the ground
state energy and emits a photon in the process.
The momentum of the photon is:
A. 2.3 x 10-27 kg.m/s
B. 1.7 x 10-27 kg.m/s
C. 4.3 x 10-27 kg.m/s
D. 2.3 x 10-27 kg.m/s
12. An electron is confined to an infinite square
well of width L. An experiment is done in which a

photon is absorbed promoting the electron from a
lower state to higher state. It is found that the
longest wavelength photon that can be absorbed is
430 nm. What is the width of the well?

A. 326 nm
C. 886 nm

B. 517 nm
D. 3100 nm

A.
B.
C.
D.

0.78 nm
0.624 nm
0.67 nm
0.93 nm

7. An electron has 15 eV of energy. Define its
frequency and the de Broglie wavelength.
15

-10

A. 2.4 x 10 Hz, 3.9 x 10 m
B. 2 x 1010 Hz, 3 x 10-12 m
C. 3.62 x 1015 Hz, 0.317 x 10-9 m

D. A and B are wrong
8. Define the de Broglie wavelength of a relative
particle moving with kinetic energy K. What is
the value of K for deviation between the relative
and nonrelative electron smaller than 1%?
A. 5.15 KeV
C. 215 KeV

B. 515 eV
D. 415 eV

9. A particle m = 5.4 x10-27 kg emitted in the
radioactive decay of uranium-238 has an energy
of 5.20 MeV. What is its de Broglie wavelength?
A. 8.5 × 10-9 m
C. 3.5 × 10-5 nm

B. 7.02 × 10-15 m
D. 0.56 × 10-14 nm

10. Which of the following sets of quantum
numbers is possible for an electron in a hydrogen
atom?
A. n = 4, l = 3, ml = -3

13. An electron in an infinite 1-D square potential
well of width 8 nm, decays from the state with
quantum number n (i.e., the n-1 excited state) to
state m. Compare the wavelengths of the emitted
photon for the two transitions: 11

10 and 5
2
A. λ11
10 < λ5
2
B.
λ11
>
λ
10
5
2
C.
λ11
10 = λ5
2
14. An electron drops from the n = 3 to the n = 2
level of an infinite square well, emitting a photon
with wavelength λA. Then it drops from the n = 2
level to the n = 1 level, emitting a photon with
wavelength λB. What is the ratio λB / λA ?
A. 1
B. 4/3
C. 5/3
D. 9/4
15. The well is 5 x 10-10 m wide. What is the
electron’s kinetic energy?
A. 3.4 x 10-21 J
B. 1.5 x 10-18 J
C. 2.4 x 10-19 J

D. 7.6 x 10-42 J


16. Four different particles are trapped in onedimensional wells with infinite potential energy at
their walls. The masses of the particles and the
width of the wells are

18. There are Urani and lead atoms in Urani ore.
Lead atoms are products of the radiation of Urani.
Half life of Urani is 4.47×109 years. How old is
the ore if the ratio between the number of Urani
and lead atoms are 5 : 1

1. mass = 4mo, width = 2Lo
2. mass = 2mo, width = 2Lo
3. mass = 4 mo, width = Lo
4. mass = mo, width = 2Lo
Rank them according to the kinetic energies of the
particles when they are in their ground states.
A. 1, 2, 3, 4
B. 1, 2, 3 and 4 tied

A.
B.
C.
D.

1.175 x 109 years
4.47 x 109 years
6.02 x 108 years

8.02 x 1018 years

19. At the initial time, during nuclear reaction of the
atom A, 45Ca are collected with the speed of 1010
atoms per s econd. Half life of A atom is 152 days.
The mass of 45Ca after 250 days is:

A. 9.63×10-3 g
B. 8.38×10-4g
C. 5.77×10-5g
D. 0.067 g

C. 1 and 2 tied, then 3, 4
D. 4, 3, 2, 1
17. A radionuclide can decay by either beta-minus
or positron emission. The two daughter nuclei are:
A. Isomers.
B. Isobars.

20. Half life of radioactive substance was
measuring by a pulse counter. Time was set zero
initially. At t1 = 4 hour, n1 pulses were collected.
At t2 = 2t1, n2 pulses were collected. The ratio
between the pulses is n2 = 1.5 n1. Half life of that
radioactive substance is:
A. T=2 hours
B. T=8 hours
C. T=6 hours
D. T=4 hours

C. Isotones.
D. Isotopes.

B. PROBLEMS:
1. A laser used to weld detached retinas emits light with a wavelength of 852 nm in pulses that are 40.0 ms
in duration. The average power during each pulse is 0.800 W.
(a) How much energy is in each pulse in joules? In electron volts?
(b) What is the energy of one photon in joules? In electron volts?
(c) How many photons are in each pulse?

2. Through what potential difference must electrons be accelerated so they will have (a) the same
wavelength as an x ray of wavelength 0.30 nm and (b) the same energy as the x ray in part (a)?
3. A hydrogen atom in the 5g state is placed in a magnetic field of 0.700 T that is in the z direction
(a) Into how many levels is this state split by the interaction of the atom’s orbital magnetic dipole
moment with the magnetic field? (b) What is the energy separation between adjacent levels? (c)
What is the energy separation between the level of lowest energy and the level of highest energy?
4. A photon with a wavelength of 3.50 x 10-13 m strikes a deuteron, splitting it into a proton and a
neutron. (a) Calculate the kinetic energy released in this interaction. (b) Assuming the two particles


share the energy equally, and taking their masses to be 1.00 u, calculate their speeds after the
photodisintegration.


Revision for Final exam 2020-2021

Nuclear physics
1. A sample of rock from the Moon was verified. The ratio between the number
of Ar 40 nuclei and the number of K 40 was 10.3. Ar 40 is known as the product
nucleus of the K 40 nuclear radioactivity. Half life of K 40 is 1.25.109 year. How

old is this rock sample?
2. From the following information calculate the minimum energy required to
separate a deuteron into its component parts (1 amu = 931.2 MeV)
Particle

amu

Proton

1.00727

Neutron

1.00866

Deuteron

2.0135

A. 1.875 MeV
C. 2.26MeV

B. 2.02 MeV
D. 2.38 MeV

E. 4.03 MeV

3. After the radiation of Pion (at rest initially), 2 nuclei: Muyon and Neutrino
are collected
𝜋 + → 𝜇+ + 𝜗

The rest energy of Pion and Muyon is 139.5 MeV; 105.7 MeV, respectively.
The total kinetic energy of the 2 product nuclei is:
a)
b)
c)
d)

2.7×10-12 J
5.4×10-12 J
1.6×10-13 J
3.39×10-12 J

Atomic physics

4. An electron is in a quantum state for which the magnitude of the orbital
angular momentum is √42ħ. How many allowed values of z component of
the angular momentum are there?
5. In Hydrogen atom, electron is in 4p of level energy. When this electron
drops to the ground state, define the change of magnitude of magnetic
dipole moment.


AW: -13.10-24 J/T

41.62/1403

Quantum Mechanics

+Wave particle duality
6/An electron sits in the 2nd energy level in an infinite 1-D well. The well is

10-12m wide. What’s the electron’s kinetic energy?
If the well were made double as wide as in the preceding problem, by what
factor would the kinetic energy change?
7/ A proton is trapped in a quantum wire that is 4 nm long (approximate a
quantum wire is a 1D infinite potential well of width 4 nm). What would
be its de Broglie wavelength in the ground state?
8/An electron drops from the n=8 to the n=5 level of an infinite square well
that is 2.10-12 m wide. What is the wavelength of the photon emitted as a
result?

+Particle in a box
9/


Quantum Optics

+Continuous spectra
10/A brick house has 1000 m2 of total area, the radiation temperature is
270C. What is the radiated energy of this house during a day? Assume this
house as a black body.
11/A black body has 105 kW of radiation power. If the wavelength related
to the greatest radiation intensity is 7.10-7 m, what is the area of the body?

+Compton scattering
12/ Electromagnetic radiation with 0.8 MeV of energy is scattered from
stationary electrons. The scatterd photons have wavelength equal to
Compton wavelength. Through what angle were the photons scattered?
AW: 500
13/ X-rays with an energy of 450 keV undergo Compton scattering from a
target. If the scattered rays are deflected at 280 relative to the direction of

the incident rays, find (a) the Compton shift at this angle, (b) the energy of
the scattered x-rays, and (c) the kinetic energy of the recoiling electron.
(Compton wavelength is 2.43×10-12 m )
14/ Electromagnetic radiation with a wavelength of 0,03.10-10 m is
scattered from stationary electrons. With scattered angle 600, 900, define
the energy that transfers to electrons.
AW: 120 keV, 186 keV
15/ Electromagnetic radiation with a wavelength of 0,03.10-10 m is
scattered from stationary electrons and photons that have been scattered
through 900 are detected. After the scattering event, what is the magnitude
of the electron’s momentum? What is an angle of moving out electron?


Special relativity


16/ A rod has a proper length of 2m. It is moving with speed 0.8c with respect to
a laboratory. It also makes an angle 30 degree relative to the direction of
moving. Define the length of the rod in the laboratory frame.


Which phenomenon is best explained by the particle nature of light?
A. The Doppler Effect
B. Polarization
C. The photoelectric effect
D. interference
According to the quantum theory of light, the energy of light is carried in discrete units called
A. alpha particles
B. photoelectrons
C. protons

D. photons
If the wave properties of a particle are difficult to observe, it is probably due to the particle's
A. small size
particle nature -> \delta x must be small,
B. large mass
\delta p must be large
C. low momentum
wave properties -> \delta p must be small,
\delta x must be large
D. high charge
If an orbiting electron falls to a lower orbit, the total energy of that atom will
A. remain the same
conservation of energy,
range is the atom itself
B. increase
-> E decreases as the
C. decrease
electron gets to lower
energy state

The energy of a photon varies directly with its
A. frequency
B. wavelength
C. speed
D. rest mass
Blue light has a frequency of approximately 6.0 x 10^14 Hz. A photon of blue light will have an energy of
A. 5.0 x 10^ -7 J
B. 4.0 x 10^ -19 J
C. 1.1 x 10^ -48 J
D. 6.0 x 10^ -34 J

Protons in the nucleus attract electrons with enough electromagnetic force to keep them in orbit at high
speeds. Protons in general repel each other, but in the nucleus they are bound together. How is this
possible?
a. The strong force binds the protons together on small distance scales.
b. The electrons orbiting the nucleus create an electromagnetic force on all sides due to their high speed
of revolution.
c. The electroweak force binds the protons together on small distance scales.
d. The introduction of neutrons diffuses the protons' charge over a large volume.
e. The gravitational force binds the protons together on small distance scales.