SCHOOL OF HEALTH AND APPLIED SCIENCES DEPARTMENT OF NATURAL AND APPLIED SCIENCES BSC PROGRAMME

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SCHOOL OF HEALTH AND APPLIED SCIENCES DEPARTMENT OF NATURAL AND APPLIED SCIENCES BSC PROGRAMME QUALIFICATION(S): Bachelor of Science (Major and Minor in Natural Sciences) QUALIFICATION CODE: 07BOSC

1 SCHOOL OF HEALTH AND APPLIED SCIENCES DEPARTMENT OF NATURAL AND APPLIED SCIENCES BSC PROGRAMME QUALIFICATION(S): Bachelor of Science (Major and Minor in Natural Sciences) QUALIFICATION CODE: 07BOSC NQF LEVEL: LEVEL 7 COURSE NAME: MODERN PHYSICS COURSE CODE: MPH60S NQF LEVEL: 6 DATE: JANUARY 06 DURATION: 3 HOURS MARKS: 00 ND OPPORTUNITY EXAMINATION QUESTION PAPER EXAMINER(S): MODERATOR: PROF. ECHI IDUGBA MATTHIAS MR. INDONGO VAINO INSTRUCTIONS:. Answer all the questions in the booklet provided. Show clearly all the steps used in the calculations 3. All written work MUST be done in blue or black ink and sketches MUST be done in pencil 4. No books, notes and other additional aids are allowed. 5. See list of useful constants at the end of this question paper PERMISSIBLE MATERIALS Non-Programmable Calculator ATTACHMENTS: None This paper consists of 6 pages including this cover page

2 SECTION A QUESTION [0] Suggested Question Types: Multiple Choice/Objectives For each question write the letter corresponding to your choice in your answer booklet Each question in this section carries mark. The peaks of the blackbody radiation spectrum shift toward higher frequencies as () A. temperature increases B. temperature decreases C. temperature remains constant D. pressure remains constant. The Rayleigh-Jean s blackbody radiation law fails in the limit () A. low frequency B. low wavelength C. long wavelength D. very low frequency.3 When photons of appropriate frequency are incident on a metal surface, electrons may be ejected from the metal surface. This is called () A. thermionic effect B. photoelectric effect C. field effect D. radioactivity.4 It is very uncomfortable to wear black dress in a very hot sun because black dress A. reflects radiation B. absorbs heat C. reflects heat D. rejects hea t ().5 All the ejected electrons in photoelectric effect experiment do not have the same velocity because () A B C D some electrons are heavier than the others the work-function a metal for each electron is different some electrons are removed from deep the surface of the metal the frequency of incident radiation is below the threshold frequency.6 The work-function of platinum metal is 6.4 ev. The minimum frequency of photon that can eject electrons from the metal surface is () A Hz B Hz C Hz D Hz.7 Which of the followings is true about the Compton Effect scattering. () A. The energy of the incident photon is all absorbed by the scattering electron B. The change in wavelength of the incident photon depends only on the angel of scattering. C. The scattered radiation has a shorter wavelength than the incident photon D. The energy of the scattered radiation is greater than the energy of the incident radiation

3 .8 A photon can split into electron-positron pair when () A. it passes through a vacuum B. it passes close to atomic nucleus C. its energy is very high D its energy is very low.9 The reaction is a good example of a () A. nuclear fusion B. nuclear decay C. nuclear fission D nuclear absorption.0 The de Broglie wavelength of an electron is m. Find the radius, r n of the Bohr orbit of the electron for n =. () A m B m C m D m. The wavelength of Lyman transition from energy level n = 5 is () A m B m C m D m. Which one of the following quantum states does not exist? () A. Ψ B. 3 Ψ C. 3 Ψ D. 33 Ψ 3.3 For energy production in a nuclear reaction the Q-value of the reaction must be () A greater than zero B equal to zero C greater than zero D very much less than zero.4 The splitting of a single energy level into three energy levels when a hydrogen atom is placed in a magnetic field is caused by the interaction of with magnetic field () A. excited electron B. dipole moment C. quadrupole moment D. magnetic moment.5 In many electron atoms the Zeeman Effect can be observed without external magnetic field because () A. the magnetic field of the nucleus acts as substitute B. the electric field of the nucleus acts as substitute C. the ionization energy of the electrons acts as substitute D. the magnetic field of electron current acts as substitute.6 The following decay Cu 8 Ni + e is an example of () A. alpha decay B. electron emission C. positron emission D. electron capture.7 The decay constant of a radionuclide is s -. How long will it take half of the sample of the radionuclide to decay? () 3

4 A. 54 hrs B. 64 hrs C. 74 hrs 84hrs.8 The intensity of radiation was reduced to half after the radiation has penetrated a depth or 0.04mm of a material. The attenuation constant of the material is () A mm - B mm - C.. mm - D mm -.9 Which of the following radiations has the highest penetrating ability? () A. beta rays B. alpha rays C. radar rays D. gamma rays.0 In which of the following samples will radiocarbon dating not work? () I Dead animal sample II Sodium chloride sample III Dead human sample IV pure rock sample A. I B. II, IV C. I, III D. II SECTION B QUESTION [0]. Define the following terms: the threshold voltage and threshold frequency for photoemission of a metal. (). The Plank spectral distribution of a blackbody is given by the expression: 3 8 πh υ dυ U( υ) dυ = h υ /k T c e 3 B.. Name the symbols h, υ, k B, c, and T with their correct units. (4).. Express the formula in wavelength space. (4)..3 Sketch on the same graph the curves of U(υ ) vs υ for T = 00 o K, 300 o K and. 400 o K. (3).3 The minimum frequency for photoelectric effect in copper is.x0 5 Hz. Find the maximum kinetic energy of the ejected electrons in electron volts when a radiation of frequecy.8 x 0 5 Hz falls on the surface of the metal. (3).4 The frequency of the scattered radiation in a Compton Effect experiment is 6.67 x 0 6 Hz. Calculate the wavelength of the incident photon if the angle of scattering is 45 o. (4) 4

5 QUESTION 3 [0] 3. State de Broglie hypothesis and the uncertainty principle. (4) 3. Explain clearly how Davisson-Germer experiment supports the de Broglie hypothesis. 3.3 The lattice spacing of crystals like sodium chloride is 0.8nm. To study such crystals energetic particles with de Broglie wavelength equal to the crystal spacing are required. Calculate the non-relativistic neutron kinetic energy in ev if it is to be used for crystal study. (4) 3.4 Derive an expression for the total energy of the hydrogen atom assuming the planetary model of electron orbit. (4) 3.5 Sketch the current voltage (I-V) characteristics of Frank-Hertz experiment and explain the significance of the result. (4) QUESTION 4 [0] 4. Explain the meaning of ferromagnetism in cobalt. Write the electronic structure of cobalt 59 Co and explain why it is ferromagnetic. (4) 7 4. Explain the origin of the magnetic moment of the electron in a hydrogen atom. Evaluate the magnitude of the magnetic moment of an orbiting electron in the first Bohr orbit if the orbital frequency is 0 3 Hz (a o = 5.9x0 - m). (4) 4.3 Explain the meaning of L-S coupling in multi-electron atoms. Explain why Zeeman effect cannot be observed in neon( 0 0 Ne) atom. (4) 4.4 Evaluate the frequency of radiation when a transition from n= to n= occurs in a hydrogen atom. Calculate all the frequencies when the atom is placed in a magnetic field of strength Tesla (E = 3.6eV) (4) 4.5 An atom in excited state has the electronic configuration s s d. Name this atom. Evaluate all the possible energy states of the atom and their term notations. (4) QUESTION 5 [0] 5. Explain two differences and one similarity between the two reactions below: U+ n Xe+ Sr n () H+ H He+ n 7.6MeV () (3) State the law of radioactive decay and obtain the solution. (3) 5.3 A piece of coal extract was found to have an activity of 3 disintegration per min per gram of its 4 6C content. The activity of living wood is 6 disintegration per min per gram. How long ago did the tree from which the coal came from die? ( t of 4 6C=5760yr). (6) 0 5

6 5.4 Explain the following terms with two examples each: isotopes, ionising radiation, nonionising radiation. (4) 5.5 Evaluate the nuclear radius of uranium 38 9U (R o =. x 0-5 m). (4) LIST OF USEFUL CONSTANTS: Electron charge, e = C Electron mass, m e = kg Plank constant, h = Js Neutron mass m n = kg Speed of light, c = ms - Rydberg s constant, R = m - Boltzmann constant, k B = JK - Bohr magneton, μ B = π = evt END 6

Physics 3204 UNIT 3 Test Matter Energy Interface

Physics 3204 UNIT 3 Test Matter Energy Interface 2005 2006 Time: 60 minutes Total Value: 33 Marks Formulae and Constants v = f λ E = hf h f = E k + W 0 E = m c 2 p = h λ 1 A= A T 0 2 t 1 2 E k = ½ mv 2