Đề thi học kì 2 môn Vật lý 2 năm 2018-2019 có đáp án - Trường Đại học Bách Khoa TP. Hồ Chí Minh (Final exam of Physics A2 - No.2) cung cấp đến các bạn sinh viên gồm những bài tập trắc nghiệm và tự luận có kèm theo đáp án, hỗ trợ cho quá trình học tập, ôn tập chuẩn bị cho kì thi sắp tới. Mời các bạn cùng tham khảo.
Trang 1National 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 No 2
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 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
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 rays D 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
Trang 2A 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 λ e < λ p B λ e > λ p C λ e = 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?
17 The electron makes a transition from the n = 2 to n = 4 level by absorbing a photon Calculate the wavelength of this photon
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
C 3.62 x 1015 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.
Trang 3b) 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 234Th by 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:
s J
= 5,67.10−8 −2 −4
σ b 2,898.10−3mK
= c 3 108m / s
=
kg
me 9 , 1 10− 31
= e =1,6.10−19C 1Ci = 3.7x1010 decays/s