Quelpr

Particulate Nature of Electromagnetic Radiation · CAPE Physics Unit 2

258 past-paper questions on Particulate Nature of Electromagnetic Radiation, part of Atomic and Nuclear Physics, from every CAPE Physics Unit 2 paper on Quelpr.

Practise Particulate Nature of Electromagnetic Radiation
  1. 7(a)2 marks· CAPE Physics Unit 2 · 2001 · Paper 1Why are the energy values of these levels negative?
  2. 7(b)(i)2 marks· CAPE Physics Unit 2 · 2001 · Paper 1An incoming electron of kinetic energy 20.0 × 10⁻¹⁹ J collides inelastically with the hydrogen electron in its ground state. Indicate, by means of vertical arrows on the left side of the energy level diagram, possible…
  3. 7(b)(ii)1 mark· CAPE Physics Unit 2 · 2001 · Paper 1What becomes of the incident electron?
  4. 7(c)(i)2 marks· CAPE Physics Unit 2 · 2001 · Paper 1An incoming photon of wavelength 1.02 × 10⁻⁷ m collides with a similar hydrogen electron in its ground state also. Calculate the energy of this photon.
  5. 7(c)(ii)1 mark· CAPE Physics Unit 2 · 2001 · Paper 1Indicate on the right side of the energy level diagram the possible level(s) to which the absorbing electron rises.
  6. 7(c)(iii)1 mark· CAPE Physics Unit 2 · 2001 · Paper 1What becomes of the incident photon?
  7. 7(c)(iv)1 mark· CAPE Physics Unit 2 · 2001 · Paper 1State what would be the case in (c)(i) if the photon had a shorter wavelength of 0.95 × 10⁻⁷ m.
  8. 3(b)(i)5 marks· CAPE Physics Unit 2 · 2001 · Paper 2Electrons are accelerated through a potential difference of 40 000 V before striking a target to produce X-rays. Calculate the minimum cut-off wavelength λ_0 produced.
  9. 3(b)(ii)1 mark· CAPE Physics Unit 2 · 2001 · Paper 2State what change occurs in λ_0 if the accelerating potential difference is doubled.
  10. 8(a)(i)4 marks· CAPE Physics Unit 2 · 2001 · Paper 2Discuss the physical process described by E_2 - E_1 = hf and state what EACH term represents.
  11. 8(a)(ii)4 marks· CAPE Physics Unit 2 · 2001 · Paper 2Explain what is meant by 'work function'. State the energy transformation that takes place when light is incident on a surface causing electron emission, and give an equation relating the relevant quantities.
  12. 8(b)(i)3 marks· CAPE Physics Unit 2 · 2001 · Paper 2Determine the energy of each photon emitted.
  13. 8(b)(ii)4 marks· CAPE Physics Unit 2 · 2001 · Paper 2Determine the number of photons emitted per second.
  14. 8(c)5 marks· CAPE Physics Unit 2 · 2001 · Paper 2If the light is incident on a surface with work function 2.05 eV, state whether electrons will be emitted, and if so, calculate their maximum kinetic energy. (1 eV = 1.6 × 10^(-19) J)
  15. 7(a)(i)1 mark· CAPE Physics Unit 2 · 2002 · Paper 1Write an equation relating the energy E associated with a photon to its wavelength λ.
  16. 7(a)(iii)2 marks· CAPE Physics Unit 2 · 2002 · Paper 1Hence, derive the de Broglie equation which suggests the wave-particle nature of light.
  17. 7(b)(i)4 marks· CAPE Physics Unit 2 · 2002 · Paper 1Calculate its de Broglie wavelength.
  18. 7(b)(ii)2 marks· CAPE Physics Unit 2 · 2002 · Paper 1An oscillating molecule de-excites from one allowed energy level to the next lower one, changing energy by 2.2 eV. Calculate the frequency of the emitted radiation.
  19. 8(a)(i)1 mark· CAPE Physics Unit 2 · 2002 · Paper 1State the name given to the effect of using electromagnetic radiation to cause electrons to be emitted from a metal surface.
  20. 8(a)(ii)5 marks· CAPE Physics Unit 2 · 2002 · Paper 1Explain how the photoelectric effect provided evidence for the particle nature of electromagnetic radiation.
  21. 8(b)(i)1 mark· CAPE Physics Unit 2 · 2002 · Paper 1Determine the threshold frequency from the graph.
  22. 8(b)(ii)1 mark· CAPE Physics Unit 2 · 2002 · Paper 1Determine the work function from the graph.
  23. 8(b)(iii)2 marks· CAPE Physics Unit 2 · 2002 · Paper 1Determine Planck's constant from the graph.
  24. 3(a)(i)3 marks· CAPE Physics Unit 2 · 2002 · Paper 2Use the graph grid provided on page 8 to plot a graph of current versus voltage for the metal.
  25. 3(a)(ii)1 mark· CAPE Physics Unit 2 · 2002 · Paper 2From the plotted graph, record the stopping potential for the metal.
  26. 7(a)3 marks· CAPE Physics Unit 2 · 2003 · Paper 1State THREE experimental facts about the photoelectric effect which support the particulate (photon) model of light.
  27. 7(b)1 mark· CAPE Physics Unit 2 · 2003 · Paper 1When ultraviolet light is incident on an insulated metal plate, the plate emits electrons for a while and then stops. Explain why the process eventually stops.
  28. 7(c)(i)1 mark· CAPE Physics Unit 2 · 2003 · Paper 1Determine the amount of energy it will take to ionize an electron from the ground state.
  29. 7(c)(ii)1 mark· CAPE Physics Unit 2 · 2003 · Paper 1State what will happen if a 6 eV photon strikes the atom.
  30. 7(d)(i)2 marks· CAPE Physics Unit 2 · 2003 · Paper 1Calculate the frequency of radiation emitted.
  31. 7(d)(ii)1 mark· CAPE Physics Unit 2 · 2003 · Paper 1Calculate the wavelength of radiation emitted.
  32. 7(d)(iii)1 mark· CAPE Physics Unit 2 · 2003 · Paper 1In which region of the electromagnetic spectrum would this radiation be found?
  33. 8(a)(i)2 marks· CAPE Physics Unit 2 · 2003 · Paper 1Explain the principle by which a continuous X-ray spectrum is produced.
  34. 8(a)(ii)2 marks· CAPE Physics Unit 2 · 2003 · Paper 1Why is a vacancy in an inner electron shell usually required for an atom to emit an X-ray photon?
  35. 8(b)(i)1 mark· CAPE Physics Unit 2 · 2003 · Paper 1Write an expression for the emerging intensity, I, in terms of I_0, mu_1 and x_1.
  36. 8(ii)a)3 marks· CAPE Physics Unit 2 · 2003 · Paper 1Show that the Intensity, I, is given by I = I_0 e^{-(mu_1 x_1 + mu_2 x_2)}.
  37. 8(ii)b)2 marks· CAPE Physics Unit 2 · 2003 · Paper 1Calculate the value of I where I_0 = 500 W m^-2, mu_1 = 8.0 m^-1, x_1 = 2.0 mm, mu_2 = 4.0 m^-1, x_2 = 4.0 mm.
  38. 3(a)2 marks· CAPE Physics Unit 2 · 2003 · Paper 2Complete Table 2 to show the missing frequency values.
  39. 3(b)3 marks· CAPE Physics Unit 2 · 2003 · Paper 2On the graph paper on page 9, plot a graph of stopping potential, V_s, versus frequency, f.
  40. 3(c)(i)3 marks· CAPE Physics Unit 2 · 2003 · Paper 2From the graph, determine Planck's constant.
  41. 3(c)(ii)2 marks· CAPE Physics Unit 2 · 2003 · Paper 2From the graph, determine the work function, in eV, of calcium.
  42. 8(a)(i)2 marks· CAPE Physics Unit 2 · 2003 · Paper 2Explain what is meant by wave-particle duality.
  43. 8(a)(ii)3 marks· CAPE Physics Unit 2 · 2003 · Paper 2Explain what is meant by de-Broglie hypothesis.
  44. 8(a)(iii)3 marks· CAPE Physics Unit 2 · 2003 · Paper 2Explain what is meant by the photoelectric effect.
  45. 8(b)(i)2 marks· CAPE Physics Unit 2 · 2003 · Paper 2Find its threshold wavelength.
  46. 8(b)(ii)3 marks· CAPE Physics Unit 2 · 2003 · Paper 2Find the maximum energy of the photoelectrons when the metal is illuminated by light of wavelength 4 x 10^-7 m.
  47. 8(b)(iii)2 marks· CAPE Physics Unit 2 · 2003 · Paper 2Find the stopping potential.
  48. 8(c)5 marks· CAPE Physics Unit 2 · 2003 · Paper 2Explain whether or not red light will cause electrons to be emitted from sodium in (b).
  49. 7(b)5 marks· CAPE Physics Unit 2 · 2004 · Paper 1Electrons accelerated through a potential difference of 50 kV strike a target producing X-rays. Calculate the value of the cut-off wavelength λ0.
  50. 8(a)(i)2 marks· CAPE Physics Unit 2 · 2004 · Paper 1Explain what is meant by the term 'wave-particle duality of matter'.
  51. 8(a)(ii)2 marks· CAPE Physics Unit 2 · 2004 · Paper 1Give TWO examples to support the concept of wave-particle duality.
  52. 8(b)(i)2 marks· CAPE Physics Unit 2 · 2004 · Paper 1Write de-Broglie's equation and explain EACH of the symbols in the equation.
  53. 8(b)(ii)4 marks· CAPE Physics Unit 2 · 2004 · Paper 1Find the de-Broglie wavelength of electrons with kinetic energy 10 keV.
  54. 3(a)4 marks· CAPE Physics Unit 2 · 2004 · Paper 2Show that the photoelectric equation hf - Φ = (1/2)m_e v^2 can be written as V = (hc/e)(1/λ) - (hc/e)(1/λ_0), where V is stopping potential, c is speed of light, e is electron charge, λ is wavelength of light used, and…
  55. 3(b)(i)3 marks· CAPE Physics Unit 2 · 2004 · Paper 2Use the graph in Figure 3b to determine Planck's constant.
  56. 3(b)(ii)3 marks· CAPE Physics Unit 2 · 2004 · Paper 2Use the graph in Figure 3b to determine the cut-off wavelength λ_0.
  57. 8(a)(i)3 marks· CAPE Physics Unit 2 · 2004 · Paper 2Explain the term: Continuous x-ray spectrum.
  58. 8(a)(ii)3 marks· CAPE Physics Unit 2 · 2004 · Paper 2Explain the term: Characteristic x-ray spectrum.
  59. 8(a)(iii)2 marks· CAPE Physics Unit 2 · 2004 · Paper 2Explain the term: Cut-off wavelength.
  60. 8(b)(i)4 marks· CAPE Physics Unit 2 · 2004 · Paper 2Calculate the photon energies corresponding to K_β and K_α in eV.
  61. 8(b)(ii)4 marks· CAPE Physics Unit 2 · 2004 · Paper 2Determine which substance from the table could be used as a filter to absorb the K_β line much more strongly than the K_α line, and explain your answer.
  62. 8(b)(iii)4 marks· CAPE Physics Unit 2 · 2004 · Paper 2Calculate the cut-off wavelength in picometers for molybdenum.
  63. 7(a)3 marks· CAPE Physics Unit 2 · 2005 · Paper 1Sketch the typical intensity-wavelength X-ray spectrum for molybdenum, clearly indicating the minimum continuous X-ray wavelength, lambda_min, and the characteristic peaks in intensity.
  64. 7(b)2 marks· CAPE Physics Unit 2 · 2005 · Paper 1Explain the origin of the characteristic peaks observed in your sketch in (a).
  65. 7(c)3 marks· CAPE Physics Unit 2 · 2005 · Paper 1One of the K-shell electrons is removed from the atom by electron bombardment and its vacancy is filled by an M-shell electron. Calculate the wavelength of the emitted X-rays.
  66. 7(d)2 marks· CAPE Physics Unit 2 · 2005 · Paper 1The tube is operated from a 25 kV supply. What is the minimum wavelength of the continuous spectrum of X-rays?
  67. 8(a)(i)3 marks· CAPE Physics Unit 2 · 2005 · Paper 2Define the terms: 'work function', 'threshold frequency', and 'stopping potential' as applied in describing the photoelectric effect.
  68. 8(a)(ii)1 mark· CAPE Physics Unit 2 · 2005 · Paper 2What property of light does the photoelectric effect display?
  69. 8(b)(i)2 marks· CAPE Physics Unit 2 · 2005 · Paper 2What conclusions can be drawn from this plot?
  70. 8(b)(ii)2 marks· CAPE Physics Unit 2 · 2005 · Paper 2Explain how the maximum kinetic energy and maximum velocity of the photoelectrons can be deduced from this plot.
  71. 8(c)(i)2 marks· CAPE Physics Unit 2 · 2005 · Paper 2Calculate the intensity of light available for the photoelectric effect.
  72. 8(c)(ii)4 marks· CAPE Physics Unit 2 · 2005 · Paper 2Calculate the number of electrons emitted per second.
  73. 8(c)(iii)3 marks· CAPE Physics Unit 2 · 2005 · Paper 2Calculate the work function in electron volts for iron.
  74. 8(c)(iv)3 marks· CAPE Physics Unit 2 · 2005 · Paper 2Calculate the stopping potential for this radiation.
  75. 8(a)2 marks· CAPE Physics Unit 2 · 2006 · Paper 1Show on the screen of Figure 10 the diffraction pattern observed when electrons pass through the graphite sheet.
  76. 8(c)3 marks· CAPE Physics Unit 2 · 2006 · Paper 1Calculate the de Broglie wavelength of the electrons emitted from the anode.
  77. 8(d)2 marks· CAPE Physics Unit 2 · 2006 · Paper 1Describe what changes would be observed in the diffraction pattern on the screen if the accelerating voltage were decreased.
  78. 9(c)4 marks· CAPE Physics Unit 2 · 2006 · Paper 1Calculate the wavelength of the photon emitted when an electron in a mercury atom makes a transition from Level n = 3 (-3.7 eV) down to Level n = 2 (-5.5 eV).
  79. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2007 · Paper 1Which of the following phenomena led to the discovery of the particle nature of electromagnetic radiation?
  80. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2007 · Paper 1A T.V. station broadcasts at a rate 200\text{ kW} and frequency 200\text{ MHz}. How many photons are emitted every second?
  81. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2007 · Paper 1A work function of a metal is the
  82. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2007 · Paper 1The maximum wavelength of electromagnetic radiation that causes emission of photoelectrons from a metal, X, is 600\text{ nm}. What is the work function of X?
  83. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2007 · Paper 1The figure below shows an energy level diagram for a hydrogen atom. An electron moves from one energy state to another with the production of a photon of frequency 2.46 \times 10^{15}\text{ Hz}. Which energy…
  84. Q361 mark · multiple choice· CAPE Physics Unit 2 · 2007 · Paper 1This graph illustrates the x-ray spectrum from a given x-ray tube. What do X, Y and Z represent?
  85. Q371 mark · multiple choice· CAPE Physics Unit 2 · 2007 · Paper 1p is the momentum of a particle and \lambda is its wavelength. For which of the following graphs would the gradient be equal to the Planck's constant?
  86. 9(a)3 marks· CAPE Physics Unit 2 · 2007 · Paper 2Explain the meaning of 'photoelectric effect' and discuss why the existence of a threshold cut-off frequency provides evidence for the particle model of light over the wave model.
  87. 9(b)(i)4 marks· CAPE Physics Unit 2 · 2007 · Paper 2Calculate the number of photons incident on the illuminated surface per second.
  88. 9(b)(ii)3 marks· CAPE Physics Unit 2 · 2007 · Paper 2Calculate the number of photoelectrons emitted per second.
  89. 9(c)(i)2 marks· CAPE Physics Unit 2 · 2007 · Paper 2Explain how the maximum kinetic energy of the photoelectrons can be determined experimentally.
  90. 9(c)(ii)3 marks· CAPE Physics Unit 2 · 2007 · Paper 2Write down the photoelectric equation based on the conservation of energy and define each term in the equation.
  91. 9(c)(iii)3 marks· CAPE Physics Unit 2 · 2007 · Paper 2Use the photoelectric equation to calculate the threshold wavelength for photo-emission from the metal.
  92. 9(c)(iv)2 marks· CAPE Physics Unit 2 · 2007 · Paper 2State, with a reason, whether photoelectric emission will occur when light of wavelength 680 nm is incident on this metal surface.
  93. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2007 (Specimen) · Paper 1Which of the following phenomena BOTH demonstrate the wave nature of matter?
  94. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2007 (Specimen) · Paper 1In which of the following radiations do the photons have the LEAST energy?
  95. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2007 (Specimen) · Paper 1Photoelectrons are emitted from the surface of zinc metal when light of intensity, I, and wavelength, \lambda, is incident on it. What is the effect on the work function of the zinc metal if the intensity is doubled…
  96. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2007 (Specimen) · Paper 1E.M. radiation is produced when very high speed electrons strike a hard target. This type of electromagnetic radiation is known as
  97. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2007 (Specimen) · Paper 1Which of the following graphs correctly show the relationship between the energy, E, of photons of light and their wavelength?
  98. Q361 mark · multiple choice· CAPE Physics Unit 2 · 2007 (Specimen) · Paper 1A beam of electrons are made to strike a thin layer of carbon in an evacuated tube as shown in the diagram above. This experiment provides evidence for
  99. Q371 mark · multiple choice· CAPE Physics Unit 2 · 2007 (Specimen) · Paper 1An object of mass m has kinetic energy, E_k. Which of the following is a correct expression for its de Broglie wavelength?
  100. Q391 mark · multiple choice· CAPE Physics Unit 2 · 2007 (Specimen) · Paper 1In an experiment to investigate photoelectricity a graph of stopping potential of photoelectrons is plotted against frequency of incident radiation. What is the MAXIMUM kinetic energy of photoelectrons emitted by…
  101. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 1Light falls on a photoelectric material and no electrons are emitted. Which of the following quantities when increased will cause electrons to be emitted? I. Intensity of the light II. Frequency of the light III.…
  102. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 1Which scientist proposed a quantum theory to explain the photoelectric effect?
  103. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 1Compared to a 10\text{ eV} photon, a 2\text{ eV} photon has a
  104. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 1An aluminium surface having a work function of 6.7 \times 10^{-19}\text{ J} is illuminated with radiation of wavelength 250\text{ nm}. Calculate the maximum kinetic energy of the emitted photoelectrons.
  105. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 1The DeBroglie equation is
  106. Q361 mark · multiple choice· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 1A student attempts to determine the linear absorption coefficient \mu of an X-ray absorber. The incident radiation at the surface is 64\text{ counts per second} and the transmitted radiation after passing through…
  107. Q441 mark · multiple choice· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 1The energy required for an electron to move from the ground state and leave the atom would be
  108. 3(a)(i)1 mark· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 2Add a curve to Figure 3a showing the effect of increasing the light intensity, and label it A.
  109. 3(a)(ii)1 mark· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 2Add another curve to Figure 3a labelled B showing the expected result if radiation with shorter wavelength is used.
  110. 3(a)(iii)2 marks· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 2Explain why the current stays constant between X and Y on the graph.
  111. 3(a)(iv)1 mark· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 2Explain why the current decreases when the voltage across the tube is reversed (region XZ).
  112. 3(a)(v)1 mark· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 2State how the stopping potential can be used to calculate the maximum kinetic energy of the photoelectrons.
  113. 3(b)(i)7 marks· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 2Plot a suitable graph on the grid provided using the given data of E_{\max} and frequency f, and determine the value of Planck's constant h.
  114. 3(b)(ii)2 marks· CAPE Physics Unit 2 · 2008 (Rest of Region) · Paper 2Calculate the value of the work function for this photocathode.
  115. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2008 (T&T) · Paper 1Which of the following gives the correct equation for the energy (E) of a photon?
  116. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2008 (T&T) · Paper 1An electron has kinetic energy of 8 \times 10^{-18}\text{ J}. What is this value in electron-volts?
  117. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2008 (T&T) · Paper 1A metal surface has a work function of 3.8\text{ eV}. Determine the threshold wavelength for this metal.
  118. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2008 (T&T) · Paper 1Item 34 refers to the following diagram. The graph above shows what happens when light of frequency 7.5 \times 10^{14}\text{ Hz} is incident on a metallic surface. The work function for the metal is
  119. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2008 (T&T) · Paper 1Item 35 refers to the following diagram which shows some of the electron energy levels in a hydrogen atom. What is the energy required to ionize a hydrogen atom?
  120. Q361 mark · multiple choice· CAPE Physics Unit 2 · 2008 (T&T) · Paper 1In the photoelectric effect, the work function is
  121. Q371 mark · multiple choice· CAPE Physics Unit 2 · 2008 (T&T) · Paper 1If each of the following particles are moving at 0.2\ c, where c is the speed of electromagnetic radiation, which particle has the longest de Broglie wavelength associated with it?
  122. 3(a)(i)1 mark· CAPE Physics Unit 2 · 2008 (T&T) · Paper 2Explain what is meant by the 'stopping potential'.
  123. 3(a)(ii)2 marks· CAPE Physics Unit 2 · 2008 (T&T) · Paper 2With reference to Figure 4, explain how the stopping potential may be measured.
  124. 3(b)(i)1 mark· CAPE Physics Unit 2 · 2008 (T&T) · Paper 2Complete Table 2 by filling in the missing values of 1/\lambda.
  125. 3(b)(ii)3 marks· CAPE Physics Unit 2 · 2008 (T&T) · Paper 2On the grid provided, plot a graph of stopping potential, V_s against 1/\lambda.
  126. 3(b)(iii)a)4 marks· CAPE Physics Unit 2 · 2008 (T&T) · Paper 2Use the graph to determine Planck's constant.
  127. 3(b)(iii)b)2 marks· CAPE Physics Unit 2 · 2008 (T&T) · Paper 2Use the graph to determine the cut-off wavelength, \lambda_0.
  128. 3(b)(iii)c)2 marks· CAPE Physics Unit 2 · 2008 (T&T) · Paper 2Use the graph to determine the work function of the metal.
  129. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2009 · Paper 1Light falls on a photoelectric material and no electrons are emitted. Electrons may be emitted if which of the following is/are increased? I. The intensity of the light II. The frequency of the light III. The…
  130. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2009 · Paper 1Item 32 refers to the diagram below which shows a photocell, consisting of an anode A and a cathode C inside an evacuated glass tube, connected to an ammeter, voltmeter and a variable d.c. power supply. When the…
  131. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2009 · Paper 1A metal surface has a work function of 3.8\text{ eV}. The threshold wavelength for this metal is
  132. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2009 · Paper 1The intensity of X-rays passing through a material of thickness, x, is given by I = I_0 \exp(-\mu x). What does the symbol "\mu" in the equation represent?
  133. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2009 · Paper 1Item 35 refers to the drawing below which shows an energy level diagram for hydrogen. What is the energy required to ionize a hydrogen atom in its ground state?
  134. Q361 mark · multiple choice· CAPE Physics Unit 2 · 2009 · Paper 1Which of the following demonstrates the particle nature of electromagnetic radiation?
  135. 3(a)(i)3 marks· CAPE Physics Unit 2 · 2009 · Paper 2Einstein's photoelectric equation is given by K_max = h*f - phi. Clearly explain each term used in this equation.
  136. 3(a)(ii)2 marks· CAPE Physics Unit 2 · 2009 · Paper 2Sketch a labelled graph of photocurrent versus applied voltage for two light intensities I1 and I2 (where I2 > I1), clearly marking the stopping potential.
  137. 3(b)(i)1 mark· CAPE Physics Unit 2 · 2009 · Paper 2Complete the table by calculating and filling in the values of frequency f corresponding to each wavelength.
  138. 3(b)(ii)3 marks· CAPE Physics Unit 2 · 2009 · Paper 2Plot a graph of stopping potential Vs versus frequency f on the grid provided and draw the best straight line through the points.
  139. 3(b)(iii)a)3 marks· CAPE Physics Unit 2 · 2009 · Paper 2From your plotted graph, determine Planck's constant.
  140. 3(b)(iii)b)1 mark· CAPE Physics Unit 2 · 2009 · Paper 2From your plotted graph, determine the threshold frequency.
  141. 3(b)(iii)c)2 marks· CAPE Physics Unit 2 · 2009 · Paper 2From your plotted graph, determine the work function of the metal.
  142. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2010 · Paper 1Which of the following observations is/are associated with the photoelectric effect? I. Photoelectrons are emitted from the surface of the metal as soon as light of frequency greater than the threshold frequency is…
  143. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2010 · Paper 1Which scientist proposed a quantum theory to explain the photoelectric effect?
  144. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2010 · Paper 1A metal surface has a work function of 3.8\text{ eV}. Determine the threshold wavelength for this metal.
  145. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2010 · Paper 1Which of the following graphs represents the correct relationship between photoelectric current and intensity of incident radiation?
  146. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2010 · Paper 1An experiment to investigate the photoelectric effect was performed and a graph of energy of photoelectrons vs frequency of incident radiation plotted as shown below. If e is electronic charge, V_s is stopping…
  147. 6(a)(i)3 marks· CAPE Physics Unit 2 · 2010 · Paper 2With the aid of a sketch graph, clearly explain Continuous X-ray spectrum and how it originates.
  148. 6(a)(ii)2 marks· CAPE Physics Unit 2 · 2010 · Paper 2With the aid of the sketch graph, clearly explain Characteristic X-ray spectrum and how it originates.
  149. 6(a)(iii)2 marks· CAPE Physics Unit 2 · 2010 · Paper 2With the aid of the sketch graph, clearly explain Cut-off wavelength and how it originates.
  150. 6(b)(iii)3 marks· CAPE Physics Unit 2 · 2010 · Paper 2Calculate the cut-off wavelength of the X-rays emitted.
  151. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2011 · Paper 1Light falls on a photoelectric material and no electrons are emitted. Electrons may be emitted if which of the following is/are increased? I. The intensity of the light II. The frequency of the light III. The…
  152. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2011 · Paper 1What does the symbol, \Phi, represent in the equation hf = \Phi + E_{\text{max}}?
  153. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2011 · Paper 1A metal surface has a work function of 3.8\text{ eV}. What is the threshold wavelength for this metal?
  154. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2011 · Paper 1The intensity of X-rays passing through a material of thickness, x, is given by I = I_0 \exp(-\mu x). What does the symbol "\mu" in the equation represent?
  155. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2011 · Paper 1What is the de Broglie wavelength of an olympic sprinter of mass 60\text{ kg} when running at a speed of 10\text{ m s}^{-1}?
  156. 6(c)1 mark· CAPE Physics Unit 2 · 2011 · Paper 2Hence comment on the sustainability of using oil as an energy source for the next century.
  157. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2012 · Paper 1When the photocell is illuminated with ultraviolet light and photoelectrons are emitted, corresponding current and voltage values are plotted. Which graph correctly shows the relationship between I and V?
  158. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2012 · Paper 1Which scientist proposed a quantum theory to explain the photoelectric effect?
  159. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2012 · Paper 1In an experiment investigating the photoelectric emissions from a metal, the stopping potential was found to be 3.0\text{ V} when light of frequency 7.5 \times 10^{14}\text{ Hz} was used. What is the work function…
  160. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2012 · Paper 1What is the linear absorption coefficient of a material of thickness 10\text{ cm} that reduces the incident X-ray intensity to half of its original value?
  161. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2012 · Paper 1An experiment to investigate the photoelectric effect was performed and a graph of energy of photoelectrons versus frequency of incident radiation plotted as shown below. If e is electronic charge, V_s is stopping…
  162. Q361 mark · multiple choice· CAPE Physics Unit 2 · 2012 · Paper 1Which of the following demonstrate the particle nature of electromagnetic radiation?
  163. 3(a)(i)1 mark· CAPE Physics Unit 2 · 2012 · Paper 2State the name of the scientist credited with the explanation of the photoelectric effect.
  164. 3(a)(ii)a)1 mark· CAPE Physics Unit 2 · 2012 · Paper 2Explain what is meant by 'threshold frequency' with reference to the photoelectric effect.
  165. 3(a)(ii)b)1 mark· CAPE Physics Unit 2 · 2012 · Paper 2Explain what is meant by 'work function' with reference to the photoelectric effect.
  166. 3(b)(i)1 mark· CAPE Physics Unit 2 · 2012 · Paper 2Fill in the missing values of frequency in Table 2.
  167. 3(b)(ii)4 marks· CAPE Physics Unit 2 · 2012 · Paper 2On the grid provided on page 11, plot a graph of stopping potential energy versus frequency for the metal.
  168. 3(b)(iii)a)4 marks· CAPE Physics Unit 2 · 2012 · Paper 2Use your graph to determine the value of Planck's constant.
  169. 3(b)(iii)b)3 marks· CAPE Physics Unit 2 · 2012 · Paper 2Use your graph to determine the work function of the metal.
  170. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2013 · Paper 1Light falls on a photoelectric material and no electrons are emitted. Electrons may be emitted if which of the following is/are increased? I. The intensity of the light II. The frequency of the light III. The…
  171. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2013 · Paper 1When the photocell is illuminated with ultraviolet light and photoelectrons are emitted, corresponding current and voltage values are plotted. Which graph correctly shows the relationship between I and V?
  172. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2013 · Paper 1A metal surface has a work function of 3.8\text{ eV}. What is the threshold wavelength for this metal?
  173. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2013 · Paper 1An electron has kinetic energy of 8 \times 10^{-18}\text{ J}. What is this value in electron-volts?
  174. Q361 mark · multiple choice· CAPE Physics Unit 2 · 2013 · Paper 1Which of the following demonstrates the particle nature of electromagnetic radiation?
  175. 3(a)3 marks· CAPE Physics Unit 2 · 2013 · Paper 2Describe the phenomenon of 'photoelectric emission'.
  176. 3(b)2 marks· CAPE Physics Unit 2 · 2013 · Paper 2Identify the property of a light source that would make it suitable for a demonstration of this phenomenon and give a reason why this property makes it suitable.
  177. 3(c)3 marks· CAPE Physics Unit 2 · 2013 · Paper 2Calculate the energy (in eV) of a light photon of wavelength 200 nm.
  178. 3(d)3 marks· CAPE Physics Unit 2 · 2013 · Paper 2Calculate the maximum velocity of the electrons ejected from the surface.
  179. 3(e)(i)3 marks· CAPE Physics Unit 2 · 2013 · Paper 2On the grid provided, plot a graph of V_s against λ. Ensure that the λ scale extends to 550 nm.
  180. 3(e)(ii)1 mark· CAPE Physics Unit 2 · 2013 · Paper 2From the graph determine the cut-off wavelength for Caesium.
  181. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2014 · Paper 1An atom makes a transition from an energy state, E_2, to a lower energy state, E_1. Which of the following expressions gives the frequency of radiation emitted in terms of Planck's constant, h?
  182. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2014 · Paper 1Which scientist used the quantum theory to explain the photoelectric effect?
  183. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2014 · Paper 1A metal surface has a work function of 3.8\text{ eV}. Determine the threshold wavelength for this metal.
  184. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2014 · Paper 1What is the linear absorption coefficient of a material of thickness 10\text{ cm} that reduces the incident X-ray intensity to half of its original value?
  185. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2014 · Paper 1An experiment to investigate the photoelectric effect was performed and a graph showing the energy of photoelectrons versus frequency of incident radiation plotted as shown below. If e is electronic charge, V_s is…
  186. 6(a)8 marks· CAPE Physics Unit 2 · 2014 · Paper 2With the aid of a CLEARLY LABELLED diagram, describe the way in which x-rays are usually produced for use in diagnostic medicine and dentistry.
  187. 6(b)3 marks· CAPE Physics Unit 2 · 2014 · Paper 2Express the energies of x-ray photons of wavelength 10^{-11}\text{ metres} in electron Volts.
  188. 6(c)4 marks· CAPE Physics Unit 2 · 2014 · Paper 2The absorption coefficient of x-rays in a hypothetical material is 0.3\text{ cm}^{-1} at the wavelength used in 6(b). What thickness of the material would be required to attenuate the intensity of a beam of x-rays to…
  189. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2015 · Paper 1A monochromatic light source emits 0.5\text{ watts} of power. The light has a frequency of 5.0 \times 10^{15}\text{ Hz} and 1\% of the photons fall on a photocell. The number of photons incident on the photocell…
  190. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2015 · Paper 1When the photocell is illuminated with ultraviolet light and photoelectrons are emitted, corresponding current and voltage values are plotted. Which graph correctly shows the relationship between I and V?
  191. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2015 · Paper 1The intensity of X-rays passing through a material of thickness, x, is given by \[I = I_0 e^{-\mu x}.\] What does the symbol '\mu' in the equation represent?
  192. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2015 · Paper 1What is the de Broglie wavelength of an olympic sprinter of mass 60\text{ kg} when running at a speed of 10\text{ m s}^{-1}?
  193. Q371 mark · multiple choice· CAPE Physics Unit 2 · 2015 · Paper 1Each of the following particles is moving at 0.2c, where c is the speed of electromagnetic radiation. Which particle has the LONGEST de Broglie wavelength associated with it?
  194. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2016 · Paper 1What is the energy of a photon of frequency 7.0 \times 10^{14}\text{ Hz}?
  195. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2016 · Paper 1The kinetic energy of a photoelectron is given as 7\text{ eV}. The velocity of the electron is
  196. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2016 · Paper 1What is the linear absorption coefficient of a material of thickness 10\text{ cm} that reduces the incident X-ray intensity to half of its original value?
  197. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2016 · Paper 1An atom makes a transition from an energy state, E_2, to a lower energy state, E_1. Which of the following expressions gives the frequency of radiation emitted in terms of Planck's constant, h?
  198. Q361 mark · multiple choice· CAPE Physics Unit 2 · 2016 · Paper 1Which of the following statement(s) is/are true about the wave-particle duality? I. The photoelectric effect is evidence that electromagnetic radiation has a particulate nature. II. Interference is evidence that…
  199. 3(a)4 marks· CAPE Physics Unit 2 · 2016 · Paper 2X-rays are weakened by their passage through matter. Write the equation which quantifies this phenomenon, and state the meaning of EACH term in your equation.
  200. 3(b)(i)3 marks· CAPE Physics Unit 2 · 2016 · Paper 2Complete Table 3 by inserting the relevant values in Columns 3 and 4 (−\ln(I/I_0) or \ln(I/I_0)^{-1} and Total Thickness / mm).
  201. 3(b)(ii)4 marks· CAPE Physics Unit 2 · 2016 · Paper 2On the grid provided in Figure 6, plot a graph of the natural log of attenuation, \ln(I/I_0) versus total thickness.
  202. 3(b)(iii)3 marks· CAPE Physics Unit 2 · 2016 · Paper 2Use your graph to determine the linear absorption coefficient of gold in \text{cm}^{-1} at the wavelength of the incident photons.
  203. 3(b)(iv)1 mark· CAPE Physics Unit 2 · 2016 · Paper 2Suggest a reason why the linear absorption coefficient of a metal would decrease with decreasing wavelength of the incident beam.
  204. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2017 · Paper 1Which of the following statements correctly describes the photoelectric effect?
  205. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2017 · Paper 1Item 32 refers to the following diagram which shows a photocell, consisting of an anode, A, and a cathode, C, inside an evacuated glass tube, connected to an ammeter, voltmeter and a variable d.c. power supply. [Diagram…
  206. Q371 mark · multiple choice· CAPE Physics Unit 2 · 2017 · Paper 1The photon model shows that the number of photons is proportional to the
  207. Q391 mark · multiple choice· CAPE Physics Unit 2 · 2017 · Paper 1Electromagnetic radiation is incident on a metal surface whose work function is 6.4 \times 10^{-19}\text{ J}. The value of the minimum frequency of radiation which will cause electrons to be emitted is
  208. Q421 mark · multiple choice· CAPE Physics Unit 2 · 2017 · Paper 1An electron has kinetic energy of 8 \times 10^{-18}\text{ J}. What is this value in electron volts?
  209. 3(a)3 marks· CAPE Physics Unit 2 · 2017 · Paper 2Identify the parts or quantities indicated by labels P, Q, and R in Figure 4.
  210. 3(b)(i)4 marks· CAPE Physics Unit 2 · 2017 · Paper 2Determine the slope of the graph in SI units.
  211. 3(b)(ii)3 marks· CAPE Physics Unit 2 · 2017 · Paper 2Formulate the algebraic equation relating stopping potential V_s to incident frequency f using the graph in Figure 5.
  212. 3(b)(iii)1 mark· CAPE Physics Unit 2 · 2017 · Paper 2State what the slope of this graph represents physically.
  213. 3(b)(iv)4 marks· CAPE Physics Unit 2 · 2017 · Paper 2From the graph, determine the threshold wavelength for the unknown metal.
  214. Q311 mark · multiple choice· CAPE Physics Unit 2 · 2018 · Paper 1What is the energy of a photon of frequency 7.0 \times 10^{14}\text{ Hz}?
  215. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2018 · Paper 1Light falls on a photoelectric material and no electrons are emitted. Electrons may be emitted if which of the following properties of the light is/are decreased? I. Intensity II. Frequency III. Wavelength
  216. Q341 mark · multiple choice· CAPE Physics Unit 2 · 2018 · Paper 1Which of the following phenomena demonstrates the particle nature of electromagnetic radiation?
  217. Q351 mark · multiple choice· CAPE Physics Unit 2 · 2018 · Paper 1The outer electron of a lithium atom is in the -8.68\text{ eV} level. How much energy is required to ionize the atom?
  218. Q361 mark · multiple choice· CAPE Physics Unit 2 · 2018 · Paper 1Which of the following statement(s) is/are true about the wave-particle duality? I. The photoelectric effect is evidence that electromagnetic radiation has a particulate nature. II. Interference is evidence that…
  219. 6(a)3 marks· CAPE Physics Unit 2 · 2018 · Paper 2Describe the phenomenon of photoelectric emission.
  220. 6(b)(i)3 marks· CAPE Physics Unit 2 · 2018 · Paper 2Define work function and state its unit of measurement.
  221. 6(b)(ii)2 marks· CAPE Physics Unit 2 · 2018 · Paper 2Define cut-off wavelength and state its unit of measurement.
  222. 6(c)(i)4 marks· CAPE Physics Unit 2 · 2018 · Paper 2Light of wavelength λ is incident on a polished metal surface. Derive an expression for the maximum speed of the photoelectrons ejected.
  223. 6(c)(ii)3 marks· CAPE Physics Unit 2 · 2018 · Paper 2Calculate the maximum speed of the ejected photoelectron when λ = 100 nm, if the metal is tin and has a work function of 5.5 eV.
  224. Q321 mark · multiple choice· CAPE Physics Unit 2 · 2019 · Paper 1Which of the following statement(s) is/are true about the wave–particle duality? I. The photoelectric effect is evidence that electromagnetic radiation has a particulate nature. II. Interference is evidence that…
  225. Q331 mark · multiple choice· CAPE Physics Unit 2 · 2019 · Paper 1What is the linear absorption coefficient of a material of thickness 10\text{ cm} that reduces the incident X-ray intensity to half of its original value?
  226. Q371 mark · multiple choice· CAPE Physics Unit 2 · 2019 · Paper 1The photon model shows that the number of photons per unit time per unit area is proportional to the
  227. Q391 mark · multiple choice· CAPE Physics Unit 2 · 2019 · Paper 1Electromagnetic radiation is incident on a metal surface whose work function is 6.4 \times 10^{-19}\text{ J}. The value of the minimum frequency of radiation which will cause electrons to be emitted is
  228. 3(a)10 marks· Physics · Unit 2 Q3 3(a)With the aid of a fully labelled diagram, describe how X-rays are produced. Your description should include an explanation of why BOTH single line and continuous spectra are generated in this process.
  229. 3(a)(i)2 marks· Physics · Unit 2 Q3 3(a)(i)Define EACH of the following terms. Work function
  230. 3(a)(i)6 marks· Physics · Unit 2 Q3 3(a)(i)Identify the components labelled A, B, C and state the role of EACH component identified.
  231. 3(a)(ii)2 marks· Physics · Unit 2 Q3 3(a)(ii)Define the term 'stopping potential'.
  232. 3(a)(ii)1 mark· Physics · Unit 2 Q3 3(a)(ii)Threshold frequency
  233. 3(a)(iii)1 mark· Physics · Unit 2 Q3 3(a)(iii)Cut-off wavelength
  234. 3(b)4 marks· Physics · Unit 2 Q3 3(b)With reference to the apparatus in Figure 7, explain the meaning of the term 'stopping potential'.
  235. 3(b)(i)4 marks· Physics · Unit 2 Q3 3(b)(i)On the grid provided in Figure 5, plot a graph of relative intensity versus combined thickness. Draw your best smooth curve through the points.
  236. 3(b)(i)2 marks· Physics · Unit 2 Q3 3(b)(i)Using the equation f = c/λ, complete Column 3 of Table 2.
  237. 3(b)(i)4 marks· Physics · Unit 2 Q3 3(b)(i)Describe the photoelectric effect and explain how the stopping potential is related to the kinetic energy of the ejected electrons.
  238. 3(b)(ii)2 marks· Physics · Unit 2 Q3 3(b)(ii)From the graph plotted in (b)(i), determine the thickness of lead which will reduce the intensity of the X-ray beam by 95%.
  239. 3(b)(ii)3 marks· Physics · Unit 2 Q3 3(b)(ii)On the axes provided in Figure 7 on page 19, plot a graph of stopping potential, V_s, versus frequency, f. Draw the line of best fit through the points.
  240. 3(b)(ii)2 marks· Physics · Unit 2 Q3 3(b)(ii)Determine the energy of this photon, in Joules.
  241. 3(b)(ii)3 marks· Physics · Unit 2 Q3 3(b)(ii)Using the relationship between stopping potential, V_s, and maximum kinetic energy, show that v_max, the maximum speed of ejected electrons, is given by v_max = sqrt(2eV_s/m).
  242. 3(b)(iii)5 marks· Physics · Unit 2 Q3 3(b)(iii)Based on the result obtained in (b)(ii), calculate a value for µ_lead, the linear absorption coefficient of lead in m⁻¹.
  243. 3(b)(iii)3 marks· Physics · Unit 2 Q3 3(b)(iii)Use the graph in (b) (ii) to determine the threshold wavelength for the material of the photosensitive emitting plate.
  244. 3(b)(iii)2 marks· Physics · Unit 2 Q3 3(b)(iii)Calculate the maximum velocity of the photoelectrons ejected from the metal surface.
  245. 3(b)(iv)2 marks· Physics · Unit 2 Q3 3(b)(iv)Explain what is meant by the 'work function of a material'.
  246. 3(b)(v)6 marks· Physics · Unit 2 Q3 3(b)(v)Calculate the maximum velocity of the ejected photoelectrons.
  247. 3(b)(vi)6 marks· Physics · Unit 2 Q3 3(b)(vi)Calculate the slope of the graph in (b) (ii) and use it to determine a value for Planck's constant.
  248. 3(c)3 marks· Physics · Unit 2 Q3 3(c)A metal Y has a linear absorption coefficient which is 0.25 µ_lead. Show that the thickness of Y required to produce the same attenuation as T_L cm of lead is 4 T_L.
  249. 3(c)4 marks· Physics · Unit 2 Q3 3(c)Technetium-99m emits gamma-ray photons of energy 140 keV. Calculate the wavelength of these photons.
  250. 3(c)(i)2 marks· Physics · Unit 2 Q3 3(c)(i)Write the general form of the photoelectric equation and rearrange it to show the linear relationship between stopping potential, V_s, and frequency, f, as shown on the graph in Figure 8.
  251. 3(c)(ii)3 marks· Physics · Unit 2 Q3 3(c)(ii)Determine the gradient of the line in Figure 8.
  252. 3(c)(iii)3 marks· Physics · Unit 2 Q3 3(c)(iii)Determine the percentage difference between the experimental value of h/e obtained in (c) (ii) and the calculated theoretical value of h/e (using the standard values of h and e given in the answer booklet on page 4).
  253. 3(c)(iv)2 marks· Physics · Unit 2 Q3 3(c)(iv)Comment on the result obtained in (c) (iii).
  254. 3(c)(v)5 marks· Physics · Unit 2 Q3 3(c)(v)Extrapolate the line on the graph in Figure 8 on page 19, to find the intercept on the V_s axis and use this value to determine the work function of the cathode material, in joules.
  255. 3(d)6 marks· Physics · Unit 2 Q3 3(d)Calculate its wavelength, in metres.
  256. 3(d)(i)2 marks· Physics · Unit 2 Q3 3(d)(i)For EACH of the labelled regions on the graph in Figure 9, state what happens to the flow of the photocurrent and explain why this happens in EACH case. Region A
  257. 3(d)(ii)2 marks· Physics · Unit 2 Q3 3(d)(ii)Region B
  258. 3(d)(iii)3 marks· Physics · Unit 2 Q3 3(d)(iii)Region C

Related topics in Atomic and Nuclear Physics